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BIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageORIGIN OF LIFE
How life originated on earth has been a mystery for mankind. While common man generally believes that God created life, scientists believe that life could have been created by natural means. In the following discussion, we shall be assessing some of these theories. Theory of special creation Religions preach that life was created byGod
WILDLIFE MANAGEMENT & CONSERVATION Wildlife management is interdisciplinary that deals with protecting endangered and threatened species and subspecies and their habitats, as well as the non-threatened agricultural animals and game species. The Wildlife Management program emphasizes both applied and basic research in wildlife ecology, management, education and extension. APICULTURE | ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMS Honeybees are indigenous to the Eurasian and African continents and were introduced to the Americas and Australia by European settlers. In India the genus Apis has the following species: the western honey bee, Apis mellifera, the eastern honey bee, Apis cerana indica, the rock bee, Apis dorsata and the small bush bee Apis florea. The UNIO - THE FRESHWATER MUSSEL Unio is a bivalve mollusc that inhabits freshwater rivers and ponds and lakes. It burrows in a furrow in sand with the help of a hatchet-shaped foot, keeping the inhalant and exhalent siphons above the sandy surface for maintaining a current of water. It is a filter feeder of planktons which are trapped by the PROTOSTOMES & DEUTEROSTOMES On the basis of embryonic development, metazoans are divided into Protostomia and Deuterostomia. Protostomes are primitive invertebrates while deuterostomes include echinoderms and chordates. This division helps in understanding relationships of different groups of animals. PROTOSTOMES Protostomes include flat worms, annelids, arthropods, molluscs and some minor phyla. KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action CRYPSIS (DECEPTION IN PREDATOR-PREY INTERACTION) Crypsis (Deception In Predator-Prey Interaction) In nature predator and prey have evolved together for millions of years. Prey must deceive the predator in order to escape getting killed, while the predator must also use deception to catch the prey unawares. NEREIS – THE CLAM WORM OR SANDWORM Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in night to prey upon small animals. N. virens (Sandworm), N. pelagica (Type-species) and N. succinea (Clam worm) are common species of Nereis. Body of Nereis is dorsoventrally flattened, segmented and 30-40 cm long having 80 to ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageORIGIN OF LIFE
How life originated on earth has been a mystery for mankind. While common man generally believes that God created life, scientists believe that life could have been created by natural means. In the following discussion, we shall be assessing some of these theories. Theory of special creation Religions preach that life was created byGod
WILDLIFE MANAGEMENT & CONSERVATION Wildlife management is interdisciplinary that deals with protecting endangered and threatened species and subspecies and their habitats, as well as the non-threatened agricultural animals and game species. The Wildlife Management program emphasizes both applied and basic research in wildlife ecology, management, education and extension. APICULTURE | ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMS Honeybees are indigenous to the Eurasian and African continents and were introduced to the Americas and Australia by European settlers. In India the genus Apis has the following species: the western honey bee, Apis mellifera, the eastern honey bee, Apis cerana indica, the rock bee, Apis dorsata and the small bush bee Apis florea. The UNIO - THE FRESHWATER MUSSEL Unio is a bivalve mollusc that inhabits freshwater rivers and ponds and lakes. It burrows in a furrow in sand with the help of a hatchet-shaped foot, keeping the inhalant and exhalent siphons above the sandy surface for maintaining a current of water. It is a filter feeder of planktons which are trapped by the PROTOSTOMES & DEUTEROSTOMES On the basis of embryonic development, metazoans are divided into Protostomia and Deuterostomia. Protostomes are primitive invertebrates while deuterostomes include echinoderms and chordates. This division helps in understanding relationships of different groups of animals. PROTOSTOMES Protostomes include flat worms, annelids, arthropods, molluscs and some minor phyla. KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action CRYPSIS (DECEPTION IN PREDATOR-PREY INTERACTION) Crypsis (Deception In Predator-Prey Interaction) In nature predator and prey have evolved together for millions of years. Prey must deceive the predator in order to escape getting killed, while the predator must also use deception to catch the prey unawares. NEREIS – THE CLAM WORM OR SANDWORM Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in night to prey upon small animals. N. virens (Sandworm), N. pelagica (Type-species) and N. succinea (Clam worm) are common species of Nereis. Body of Nereis is dorsoventrally flattened, segmented and 30-40 cm long having 80 to ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageORIGIN OF LIFE
How life originated on earth has been a mystery for mankind. While common man generally believes that God created life, scientists believe that life could have been created by natural means. In the following discussion, we shall be assessing some of these theories. Theory of special creation Religions preach that life was created byGod
WILDLIFE MANAGEMENT & CONSERVATION Wildlife management is interdisciplinary that deals with protecting endangered and threatened species and subspecies and their habitats, as well as the non-threatened agricultural animals and game species. The Wildlife Management program emphasizes both applied and basic research in wildlife ecology, management, education and extension. APICULTURE | ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMS Honeybees are indigenous to the Eurasian and African continents and were introduced to the Americas and Australia by European settlers. In India the genus Apis has the following species: the western honey bee, Apis mellifera, the eastern honey bee, Apis cerana indica, the rock bee, Apis dorsata and the small bush bee Apis florea. The UNIO - THE FRESHWATER MUSSEL Unio is a bivalve mollusc that inhabits freshwater rivers and ponds and lakes. It burrows in a furrow in sand with the help of a hatchet-shaped foot, keeping the inhalant and exhalent siphons above the sandy surface for maintaining a current of water. It is a filter feeder of planktons which are trapped by the PROTOSTOMES & DEUTEROSTOMES On the basis of embryonic development, metazoans are divided into Protostomia and Deuterostomia. Protostomes are primitive invertebrates while deuterostomes include echinoderms and chordates. This division helps in understanding relationships of different groups of animals. PROTOSTOMES Protostomes include flat worms, annelids, arthropods, molluscs and some minor phyla. KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action CRYPSIS (DECEPTION IN PREDATOR-PREY INTERACTION) Crypsis (Deception In Predator-Prey Interaction) In nature predator and prey have evolved together for millions of years. Prey must deceive the predator in order to escape getting killed, while the predator must also use deception to catch the prey unawares. NEREIS – THE CLAM WORM OR SANDWORM Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in night to prey upon small animals. N. virens (Sandworm), N. pelagica (Type-species) and N. succinea (Clam worm) are common species of Nereis. Body of Nereis is dorsoventrally flattened, segmented and 30-40 cm long having 80 to ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMSANIMAL DIVERSITY (NONCHORDATA)ANIMAL DIVERSITY (CHORDATA)ANIMAL BEHAVIOUREVOLUTIONARYBIOLOGY
Beavers – The Dam Builders. There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).ORGANIC VARIATIONS
2. Discontinuous variations: These variations deviate greatly from the average individuals. Major mutations and disruptive selection produce some individuals, which are distinct from the others. For example, white tiger, hornless calf and albino peacock or cow. Based on the inheritance, variations can be classified into the following twotypes: 1.
VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageAMERICAN MARSUPIALS
THE NEW WORLD MARSUPIALS There are some 250 species of living marsupials in the world and more than 150 fossil species are known. South American didelphoids radiated widely as carnivores and omnivores and some species in the past reached the size of a panther, e.g. Prothylacynus and the sabertooth, Thylacosmilus atrox, which wasremarkably similar
SEPIA - THE CUTTLE FISH Sepia - The cuttle fish | Zoology for IAS, IFoS and other competitive exams. Cephalopods are advanced molluscs in which foot is modified as tentacles and oral arms attached on the anterior side of the head. Sepia is a marine cephalopod found up to 3000 metre depth. They are predators and feed on fish, crabs, shrimps and prawns that they seize JAW SUSPENSION IN VERTEBRATES Jaw suspension means attachment of the lower jaw with the upper jaw or the skull for efficient biting and chewing. There are different ways in which these attachments are attained depending upon the modifications in visceral arches in vertebrates. POLYCHAETE DIVERSITY Planktonic polychaetes swim near the surface of the sea where the danger of predators and solar radiation is excessive. They generally have semitransparent body that imparts them near invisibility. Some have large eyes while others have none. Parapodia are small and locomotion is by lateral undulation of body. Cirri are generallylonger as they
KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action ORIGIN OF TETRAPODS (AMPHIBIA) The first tetrapods were amphibians that evolved from the Devonian crossopterygian fishes which lived in shallow marshy locations and already possessed lungs for respiration and lobed fins to support their bodies on muddy banks of ponds, rivers and marshland. The anatomical changes that took place during transformation from fishes to amphibia were as follows: A ZOOGEOGRAPHICAL REALMS ZOOGEOGRAPHICAL REALMS | Zoology for IAS, IFoS and other competitive exams. Sclater (1857) was the first one to give concepts of zoogeography and divided the continental masses into six Realms based on his studies on the bird fauna under two Creatio or centres of Creation, namely, Palaeogeana (Old world) and Neogeana (New world).VERTEBRATE EYE
All vertebrates have eyes that are similar in basic construction plan. This eye must have evolved very early in chordate evolution and then got modified subsequently to increase its efficiency in higher vertebrates. Vertebrate eye is a hollow ball made of three layers, outermost of which is called sclera that is made of bone, cartilageORIGIN OF LIFE
How life originated on earth has been a mystery for mankind. While common man generally believes that God created life, scientists believe that life could have been created by natural means. In the following discussion, we shall be assessing some of these theories. Theory of special creation Religions preach that life was created byGod
WILDLIFE MANAGEMENT & CONSERVATION Wildlife management is interdisciplinary that deals with protecting endangered and threatened species and subspecies and their habitats, as well as the non-threatened agricultural animals and game species. The Wildlife Management program emphasizes both applied and basic research in wildlife ecology, management, education and extension. APICULTURE | ZOOLOGY FOR IAS, IFOS AND OTHER COMPETITIVE EXAMS Honeybees are indigenous to the Eurasian and African continents and were introduced to the Americas and Australia by European settlers. In India the genus Apis has the following species: the western honey bee, Apis mellifera, the eastern honey bee, Apis cerana indica, the rock bee, Apis dorsata and the small bush bee Apis florea. The UNIO - THE FRESHWATER MUSSEL Unio is a bivalve mollusc that inhabits freshwater rivers and ponds and lakes. It burrows in a furrow in sand with the help of a hatchet-shaped foot, keeping the inhalant and exhalent siphons above the sandy surface for maintaining a current of water. It is a filter feeder of planktons which are trapped by the PROTOSTOMES & DEUTEROSTOMES On the basis of embryonic development, metazoans are divided into Protostomia and Deuterostomia. Protostomes are primitive invertebrates while deuterostomes include echinoderms and chordates. This division helps in understanding relationships of different groups of animals. PROTOSTOMES Protostomes include flat worms, annelids, arthropods, molluscs and some minor phyla. KINSHIP, SELFISHNESS AND ALTRUISM Kinship, Selfishness And Altruism. There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action CRYPSIS (DECEPTION IN PREDATOR-PREY INTERACTION) Crypsis (Deception In Predator-Prey Interaction) In nature predator and prey have evolved together for millions of years. Prey must deceive the predator in order to escape getting killed, while the predator must also use deception to catch the prey unawares. NEREIS – THE CLAM WORM OR SANDWORM Nereis or Neanthes is a marine polychaete annelid that lives in burrows in sea bottom and comes out in night to prey upon small animals. N. virens (Sandworm), N. pelagica (Type-species) and N. succinea (Clam worm) are common species of Nereis. Body of Nereis is dorsoventrally flattened, segmented and 30-40 cm long having 80 to IASZoology.com Toggle navigation* Home
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ONLINE GUIDANCE FOR THE STUDENTS OF ZOOLOGY _All Academic content is by Dr. Girish Chandra, PhD (unless otherwise stated), ex Professor, Delhi University_ * Burst of evolution takes place when animals are put into new environment. * Nothing in biology makes sense except in the light of evolution– _T. Dobzhansky_
* Contrary to Darwinism,reproduction and
_not_ survival is at the centre of evolutionary process. * Batrachotoxin, the poison from the skin of South American tree frogs, _Phyllobates and Dendrobates, _is the most toxic animal secretion known to mankind. Only 200 microgram of it is enough to killa man.
* _Natural selection__ _requires genetic
variations but natural selection also reduces genetic variations by eliminating alleles. Thus evolution by natural selection bites thehand that feeds it.
* In humans there are at least 4500 genes that cause diseases. * The combined length of blood capillaries in human body is about 96,500 kms. If blood has to fill all these capillaries, no blood will be left in arteries and veins. Therefore, body selectively supplies blood to organs that need it most. * _Natural selection_refines and
specializes a species to live in its environment but the same specializaion brings its doom when the environment changes. Thus the species also follow the cycle of birth, growth and death. * Although chimpanzee genome differs from human genome by hardly 1.5%, yet there have been 40 million evolutionary events that separated chimps from us. Read on the _Riddle of Human Origin_ * Biological evolution tracks opportunities but is blind to destinations other than survival – _ Strickburger_. Read on different _Ways of Evolution_
* Natural selection causes a change in gene frequency but is not the same as a change in gene frequency. Read details in _Hardy-Weinberg’s Law_CATEGORIES
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LATEST ARTICLES
BEAVERS – THE DAM BUILDERS There are two living species of beavers, the Eurasian, Castor fiber and the North American, Castor canadensis. Beavers belong to the mammalian family Castoridae of Rodentia that evolved in Oligocene epoch but the genus Castor evolved much later in Pleistocene, about 2 million years ago. The two living species are genetically different and have different number of chromosomes (48 in the European and 40 in the North American species). The two species are also not known to hybridize and produce viable offspring. Beavers are famous for building large dams across rivers in northern Canada by felling large trees, an amazing feat for a small animal. ...Read More
KEA – THE PREDATORY PARROT The kea (Nestor notabilis) is a parrot-like bird of family Strigopidae, which is about the size of a hen and occurs in the alpine regions of New Zealand. Their extraordinary intelligence is comparable to the primates and hence they are sometimes nicknamed 'mountain monkeys'. Being highly inquisitive, keas are notorious for exploring and manipulating objects often in residential areas where they damage articles such as shoes, car seats sofas, bags etc. with their sharp and curved beak. They are highly intelligent birds with quick learning abilities. Researchers at the Universities of Vienna and Oxford tested the Kea’s problem-solving abilities b...Read More
METHODS OF STUDYING ANIMAL BEHAVIOUR Ethology is the study of animal behaviour to find out natural responses of animals to various environmental stimuli. Some studies are also done in laboratory conditions to elicit measured responses. Therefore, ethology involves laboratory as well as field studies and has strong relationship with other sciences such as ecology, environmental science, neurology, physiology, psychology and evolution. The beginning of modern ethology commenced with the experimental as well as field studies done by the Dutch biologist Nikolas Tinbergen, Austrian biologists Konrad Lorenz and the German Karl von Frisch, who were jointly awarded Nobel Prize in 1973 for t...Read More
BIOLOGICAL RHYTHMS – CHRONOBIOLOGY Biological rhythms are self –sustaining natural cycles of animal life history which maintain themselves regardless of the environmental factors. All animals possess innate biological clocks which are driven by the biochemical mechanisms. Erwin Bunning (1936) was the first biologist to carry out extensive work on biological rhythms. CIRCANNUAL RHYTHMS They show one-year periodicity, e.g. a large number of animals reproduce once in a year. Flowering in plants also takes place once a year. Insects and amphibians follow a cycle of hibernation and activity. Hummingbirds in South America move to the caves and become inactive in winter in Andes. Famo...Read More
KINSHIP, SELFISHNESS AND ALTRUISM There are four possible types of interactions among individuals living together in a population. First, cooperation or mutualism, in which both the participants gain from the act as in the nest building by both male and female birds, or cooperation in the colony of social insects. Second, altruism in which the actor (individual that carries out the action) pays fitness cost to the recipient that gets the benefit as in social insects. Third is the selfishness, in which the actor gains but the recipient loses in terms of fitness. Fourth interaction, which is rather rare in nature, is spite in which both the participants lose in terms of fitness. A...Read More
ORIENTATION, NAVIGATION AND HOMING IN ANIMALS Orientation is the position of the animal with reference to gravity or resource. This is the position the animal maintains in order to reach the resource. Positional orientation is to maintain upright posture against gravity for which vertebrate have membranous labyrinth and invertebrate statocyst. Object orientation takes place when the animal tries to approach an object which may be food or water. Aquatic animals move vertically in pond or lake which is called strato-orientation. When the animals try to move from grassland to forests, deserts or mountains it is called zonal orientation. Animals which migrate long distances generally possess top...Read More
COURTSHIP BEHAVIOUR IN ANIMALS Courtship is a social behaviour in which there is an interaction between the male and female members of a species leading to mating and reproduction. Courtship evolved due to the fact that very large number of sperms is produced which must search and fertilise few ova leading to competition among sperms. Since males possess sperms, they must compete with one another in order to win over the female to fertilise her ova which are a limited resource. The gametic selection has translated into sexual selection among males and females, leading to male-male competition and female choice. Courtship display is an extension of this male-male competition in...Read More
SOCIAL LIFE IN PRIMATES Primates were not social animals when they evolved from the primitive insectivore ancestor in Palaeocene epoch. However, gradually primates became gregarious and social interactions developed in them leading to highly developed social life as in humans. SOLITARY PROSIMIANS Prosimians such as tarsiers, bush babies and lorises are mostly nocturnal and highly arboreal primates. Males are found solitary or in pairs with females in breeding. Females live with infants till they become independent. Prosimians are shy animals and hiding in foliage is their means of defence. They rarely come down from trees. The black coloured Aye-aye is nocturnal and li...Read More
SOCIAL ORGANISATION IN INSECTS In insects social life has evolved only in two orders, namely, Isoptera (termites) and Hymenoptera (bees, wasps and ants) which make a nest and live in colonies of thousands of individuals that practice division of labour and social interaction. SOCIAL LIFE IN TERMITES Termites were the first animals which started living in colonies and developed a well organised social system about 300 million years ago, much earlier than honey bees, ants and human beings. Although termites do not exceed 3-4 mm in size, their queen is a 4 inch long giant that lies in the royal chamber motionless, since its legs are too small to move its enormous body. Hence...Read More
CRYPSIS (DECEPTION IN PREDATOR-PREY INTERACTION) In nature predator and prey have evolved together for millions of years. Prey must deceive the predator in order to escape getting killed, while the predator must also use deception to catch the prey unawares. Crypsis is also a form of mimicry but the former has a wider meaning that includes mimicking even non-living objects such as stones, rocks, twigs and even the background. Protective colouration: Majority of the animals match the background in colour to escape the attention of the predator. For example, hares and rabbits are earth-coloured, grasshoppers are green and beach crabs have the same colour as pebbles. Counter-shading: This is als...Read More
ALARM PHEROMONES
Behaviour modifying chemicals are called semiochemicals and pheromones fall in the same category. Pheromones are chemicals which are used for communication among the members of the same species. They form the chemical language of a species. For instance, attractants are pheromones which bind the members of a colony of social insects. Kairomones are chemicals used to communicate with members of other species. For example, parasites use the host smell for searching and preys use predators’ smell to escape away. All social insects release alarm pheromones when their colony is attacked. This triggers defensive behaviour in the other members of the...Read More
DRIVE, URGE OR MOTIVATION IN ANIMALS The term Drive was introduced by Woodworth (1918) as motivational concept. Animals experienced drive as biological needs such as eating and drinking and alteration in their behaviour. Drive theories were later given by Sigmund Freud (1915) and Clark Hull (1943). Freud, who was physiologist by training, believed that drives and urges such as hunger were recurring conditions in the body of animal that produced energy build up in the nervous system. This energy build up caused psychological discomfort and restlessness that kept on increasing unless the urge was satisfied. Drive arose from a range of bodily disturbances, such as deprivation of food, ...Read More
LEARNING
Learning is the ability of the individual to remember and change one’s behaviour in response to earlier experiences. Animals learn a great deal from their surroundings and also from their experiences, particularly during the growing period. Latent learning provides animals with knowledge about their surroundings and escape routes, and also areas where food and water is available. Niko Timbergen (1951) demonstrated by experiments on digger wasp (Philanthus) that it could remember its nesting site by landmarks and got confused when landmarks were changes. W.H. Thorpe (1951) defines learning as an internal change in the animal causing adaptive cha...Read More
SIGN STIMULI
Sign stimuli, also called releasers or key stimuli, are those stimuli that are capable of releasing Fixed Action Pattern (FAP) or consummatory behaviour of the animal. They are signals that evoke instinctive patterns of behaviour in animals, such as fighting behaviour in the territorial animals, triggered by the entry of another male. Lehrman found that courting male dove began to bow and coo to a stuffed model of female in the absence of a living female. Konrad Lorenz (1972) was the first biologist to identify sign stimuli which he called key stimuli because they function as keys to release and unlock the fixed action pattern of the animal. He p...Read More
SENSORY FILTERING
Animals receive much more sensory information than they could possibly register in their brain and respond to. Therefore brain has to be selective and filter out certain information that is not so necessary. Sensory filtering or stimulus filtering takes place at several levels, namely, at the level of sense organs, nerves or different parts of brain. Sensation is the basic data sent by sense organ to brain, and sense organs have their limitation and hence filter out much of the information. For example, human eye filters out ultraviolet and infrared rays from the spectrum. Peripheral filtering is done by receptors because of their mechanical abi...Read More
NAKED MOLE RAT
The naked mole rat (Heterocephalus glaber) is a burrowing social rodent found in the grasslands of East Africa, mainly in Ethiopia, Kenya and Somalia. The unusual anatomy and social life of this bizarre animal was first studied by the German naturalist, Eduard Rüppell in 19th century, although he thought them to be mutated and deformed individuals.Anatomy. Normally the individuals are 3 to 4 inches long but the dominant queen is larger and has longer body. Fertile males are also larger than the workers and possess abdominal testes. All individuals possess almost hairless and wrinkled pinkish to yellowish skin, hence the name, naked mole rat. ...Read More
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