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Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
Section-A: Multiple choice questions (10 x 1 = 10)
1. The two chambered heart is found in
(a) Amphibian (b) Bird (c) Reptile (d) Fish
2. Fins of shark and flipper of a whale are examples of
(a) Homology (b) Analogy (c) Both a & b (d) None
3. Embryonic development is termed as
(a) Phylogeny (b) Ontogeny (c) Biogenetic (d) Recapitulation
4. Artificial selection is proposed by
(a) Von Baer (b) Darwin (c) Ernst Haeckel (d) Lamarck
5. The eras of mammals is
(a) Mesozoic (b) Coenozoic (c) Eocene (d) Permian
6. Evolution of species occurring in the different area is known as
(a) Allopatric speciation (b) Parapatric speciation (c) Sympatric speciation (d) all of them
7. The mimicry beneficial to mimic is known as
(a) Bates (b) Mullerian (c) Batesian (d) all of them
8. The geographical distribution of animal is called
(a) Flora (b) Fauna (c) Flora & Fauna (d) None of them
9. The failure of individuals to produce offspring is called
(a) Genetic load (b) Genetic death (c) Mutation (d) Both a & b
10. Parental care by brood pouches is occur in
(a) Hippocampus (b) Tilapia (c) Pholisgunnellus (d) Arius
Model Answer BSc IV Sem Zoology, Paper II
Section-B: Descriptive type
2. What is difference between gene frequency and genotype frequency? With suitable
example describe Hardy-Weinberg equilibrium.
odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour
Descriptive type: Attempts any four question (4 x 5 = 20)
. What is difference between gene frequency and genotype frequency? With suitable
Weinberg equilibrium.
Evolution and Animal Behaviour 2013
: Attempts any four question (4 x 5 = 20)
. What is difference between gene frequency and genotype frequency? With suitable
Model Answer BSc IV Sem Zoology, Paper II
odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal BehaviourEvolution and Animal Behaviour 2013
Model Answer BSc IV Sem Zoology, Paper II
3. Describe the evidences of organic evolution from comparative anatomy.
Morphological studies of various organ systems of vertebrates indicate that these are constructed
on the same basic plan. The minor differences seen in some forms are the adaptive m
to the diverse mode of living. This can be discussed under following heads:
odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour
. Describe the evidences of organic evolution from comparative anatomy.
Morphological studies of various organ systems of vertebrates indicate that these are constructed
on the same basic plan. The minor differences seen in some forms are the adaptive m
living. This can be discussed under following heads:
Evolution and Animal Behaviour 2013
Morphological studies of various organ systems of vertebrates indicate that these are constructed
on the same basic plan. The minor differences seen in some forms are the adaptive modification
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
1. Homology
2. Analogy
3. Adaptive divergence or adaptive radiation
4. Adaptive convergence
5. Vestigial organs
1. Homology:
Homology is the similarity between organs in different species or groups based on the origin
from common ancestor. Therefore, the homologous organs have common origin and are built on
the same fundamental pattern. Homology is seen in every organ system from fish to man.
Examples: Homology in limb structure of Vertebrates, Homology in brain structure, Homology
in the structure of heart.
2. Analogy:
The analogous organs have almost similar appearance and perform the same function but they
develop in totally different groups and are totally different in their basic structure and
developmental origin. Superficial resemblance is due to the performing similar function.
Examples: Analogy inforelimbs-wings of insects, pterodactyle, bird and bat; Analogy in fins-
paired fins of shark and flipper of a whale.
3. Adaptive divergence or adaptive radiation:
Adaptive radiation is exhibited by the limb structure in mammals. The limbs in mammals are
variously adapted for climbing (arboreal), flying (aerial), running, swimming or digging
(fossorial). All the limb structure are constructed on the same fundamental pattern and can be
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
derived from the prototype, pentadactyle limb structure. This is known as adaptive radiation
which represents evolution of new forms I several direction from the common ancestral type
(divergence).
4. Adaptive convergence
The whales and their relatives and the extinct reptiles, Ichthyosaurs, attained fish-like body with
their limbs modified into fins or flippers. This similarties are so marked that whale is understood
as fish by laymen. This similar body shape between animals of distantly related groups (a reptile
and a mammal) represents the phenomenon of convergent evolution. The wings of bee, bird and
bat afford another example of adaptive convergence.
5. Vestigial organs:
The vestigial or rudimentary organs are the useless remnants of structures or organs which might
have been large and functional in the ancestors. These are often undersized, degenerated and
nonfunctional.
Example: Vestigial organs in man- Vermiform appendix, auricular muscles of external ear,
nictitating membrane or plica semilunaris, vestigial tail vertebrae, wisdom teeth, body hair etc.
4. What do you mean industrial melanism? With examples of antibiotic and DDT
resistance describe the different type of natural selection.
The industrial melanism in the peppered moth, Biston betularia, provides a well studied example
of directional selection from nature. In the early part of nineteenth century there was a dramatic
rise of industrialization in Europe. The black sooty smoke fell upon the countryside and covered
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
forests and field with soot. This changed the usual colour of tree trunks from mottled greenish
grey to black.
The wing colour of the typical non melanic peppered moth was mottled grey that blended
perfectly with lichen-covered tree trunk on which moth alighted. These protected it from
enemies. Until 1948, only light colour moths were known in England. In 1948, the first dark
coloured or melanic variety of peppered moth was seen in the region of east of Manchester. This
variant was named Biston betularia carbonaria. During next 50 years, the frequency of dark
individuals gradually increased from less than 1 to about 99% in the vicinity of industrial areas.
Types of natural selection:
Based upon different organism-environment relationship, following different kinds of natural
selection have been organized:
1. Stabilizing selection
2. Directional selection
3. Disruptive selection
4. Cyclic selection
1. Stabilizing selection:
The stabilizing selection or normal selection is also called centripetal selection. It acts in the
absence of large scale environmental changes for a long period. It favors the average or normal
phenotypes and eliminates the extreme variants that fall towards both ends of the bell-shaped
Model Answer BSc IV Sem Zoology, Paper II
curve of variability for the distribution of measurements of phenotypic traits.
may be either physical or by genetic death. Example: sparrows or red checkered moth.
2. Directional selection:
Directional selection produces a regular change within a population in one direction in respect to
certain characteristics. This is due to change in the environment in particular direction.
It is progressive selection which removes more individuals from
shaped curve of variability distribution and adds towards the other end and thereby alters the
mean value of the trait in the population
occurs during or after the enviro
changes more or less in one direction over a fairly period.
1. Industrial melanism:
2. Resistance of insects to DDT:
mosquitos and houseflies is also an example of directional selection.
odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour
curve of variability for the distribution of measurements of phenotypic traits.
may be either physical or by genetic death. Example: sparrows or red checkered moth.
a regular change within a population in one direction in respect to
certain characteristics. This is due to change in the environment in particular direction.
It is progressive selection which removes more individuals from one end of the normal bell
shaped curve of variability distribution and adds towards the other end and thereby alters the
mean value of the trait in the population in a particular direction (Fig). The directional selection
occurs during or after the environmental change and the gene frequency of a particular gene
changes more or less in one direction over a fairly period. Examples:
Resistance of insects to DDT: The development of resistance to DDT or other insecticide by
s and houseflies is also an example of directional selection.
Evolution and Animal Behaviour 2013
curve of variability for the distribution of measurements of phenotypic traits. The elimination
may be either physical or by genetic death. Example: sparrows or red checkered moth.
a regular change within a population in one direction in respect to
certain characteristics. This is due to change in the environment in particular direction.
one end of the normal bell-
shaped curve of variability distribution and adds towards the other end and thereby alters the
. The directional selection
nmental change and the gene frequency of a particular gene
The development of resistance to DDT or other insecticide by
Model Answer BSc IV Sem Zoology, Paper II
3. Resistance of bacteria to drug or antibiotics: R
transferring of E. coli bacteria to increasing concentration of drug, chloroamphenicol,
the population of E coli having 250 times increased resistance to this drug. The mutant resistance
forms have better chances of survival than the nonresistance bacteria.
3. Disruptive selection:
The disruptive selection acts to break up a
different adaptive forms. It pushes the phenotype within a population away from the population
mean by supporting the value of two ends of the variability curve (Fig). It indicates that extreme
values have the highest fitness and the intermediate or mean values are relatively
disadvantageous. Examples: Sunflower population, mimetic butterflies.
odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour
Resistance of bacteria to drug or antibiotics: Role of directional selection is demonstrated by
to increasing concentration of drug, chloroamphenicol,
the population of E coli having 250 times increased resistance to this drug. The mutant resistance
forms have better chances of survival than the nonresistance bacteria.
to break up a previously homogenous population into several
different adaptive forms. It pushes the phenotype within a population away from the population
mean by supporting the value of two ends of the variability curve (Fig). It indicates that extreme
highest fitness and the intermediate or mean values are relatively
Examples: Sunflower population, mimetic butterflies.
Evolution and Animal Behaviour 2013
ole of directional selection is demonstrated by
to increasing concentration of drug, chloroamphenicol, this raised
the population of E coli having 250 times increased resistance to this drug. The mutant resistance
previously homogenous population into several
different adaptive forms. It pushes the phenotype within a population away from the population
mean by supporting the value of two ends of the variability curve (Fig). It indicates that extreme
highest fitness and the intermediate or mean values are relatively
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
4. Cyclic selection:
Selection, whether stabilizing or directional, may be constant from one generation to next if the
selective environment is not fluctuating. But when environment is not stable between generations
or between seasons, the optimum phenotype and also the optimum genotype may show
fluctuation because selection operating in direction in one generation or season may occur in
opposite direction for the next. This type of selection is called cyclic selection.
5. Define the mimicry? With suitable example describe the types and significance of
mimicry in evolution.
“Mimicry is the superficial but close resemblance of one organism to other or to some natural
objects among which it lives, that secures its concealment, protection or other advantage”, so that
it either escapes itself from observation or advertises as being harmful, which is not actually the
case. The organism which mimics is known a mimic or mimetic and the organism or objects
which is imitated or copied is called the model. The mimetic imitates other organism not only in
shape, size and colour but in action and attitude also.
Types of Mimicry:
Mimicry can be classified into three categories:
1. Protective mimicry
2. Aggressive mimicry
3. Conscious mimicry
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
1. Protective mimicry:
The protective mimicry includes those cases of imitation in which the organisms mimic models
to protect themselves from their predators. This could be obtained either by concealment or by
warning.
A. Concealing mimicry:
The organisms conceal or camouflage themselves either by altering their colouration to fit the
background or search a background which matches their colour. In certain cases they mimic the
shape and colour of other organism or object.
1. Changes in colour to match the background: Examples:
a. The white crab, Cryptolithodes, harmonises with the white pebbles on the beach.
b. Flatfishes such as plaice and sole are extremely adaptable in their skin colouration to the
background.
2. Changes the place to match the background:
When an animal is not capable of changing its colour it moves to seek out a suitable background
for resting. For example, the leaf-green animals sit on leaves, dark-coloured animal on tree-trunk
and send colored animals on the sand.
3. Mimicking the living or dead objects:
1. Indian dead-leaf butterfly, Kallima paralecta, show concealing mimicry by opening its wings
at rest resembles a dry leaf.
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
2. The stick insect, leaf insects etc.
B. Warning Mimicry:
It includes all those of protective mimicry in which the nonpoisonous and harmless organism
mimic the poisonous and harmful organism and the palatable forms resemble and advertise to be
non-palatable. This type of mimicry is helpful in self defense, because by imitating these are able
to delude and frighten the enemy and escape themselves. For example:
1. Nonpoisonous coral snakes of the family Colubridae exhibit colour pattern of poisonous coral
snakes belonging to the family Elapidae.
2. The nonpoisonous snakes of genus Heterodon flattens its head, produces frequent hissing and
strikes to advertise as it is dangerous.
3. The palatable viceroy butterfly, Lementis, mimic the distasteful or a non-palatable monarch
butterfly of the genus Danais.
C. Cryptic structures:
Animal exhibit several contrivances to delude the predator and protect themselves. For
examples:
1. Black spots or eye spots
2. Dummy head
2. Aggressive mimicry:
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
Aggressive mimicry is exhibited by carnivores animals such as fishes and spiders. These animals
either conceal themselves so that they are not easily recognized by their surroundings
(Concealment) or allure the prey (alluring). Therefore, aggressive mimicry is of two types:
a. Concealing mimicry: Examples:
1. Spider resemble in shape and color of to the flower on which they live and are thus able to pry.
2. The zone-tailed hawk (Butea albonotatus).
b. Alluring mimicry: In this mimicry, animal possesses some lure to attract its prey.
Examples: 1. Spider, 2. Angular fish
3. Conscious mimicry
Certain animals exhibit conscious imitation and on the approach of danger behave as if they are
dead bodies.
Examples: 1. American Opossum
2. Hard bodied beetles fall down like pebbles.
Significance of mimicry in evolution:
The main significance of mimicry appears to protection of individuals against enemies. This self
defense is naturally of the survival value and of evolutionary significance. It means natural
selection which is support to be most important factors in evolution, favours mimicry, since it
assure better survival and greater success in the multiplication of race.
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
6. What is difference between stereotyped and acquired animal behavior? With suitable
example describe the different types of innate behavior.
Animal behaviour may be broadly classified into two types, stereotyped and acquired type.
In stereotyped behavior, organism is to large extent stimulus bound where a pattern of stimuli
trigger a sequence of responses. Since this kind of behavior is essentially a outcome of inherited
property of nervous system of the organism, it also known as innate or inborn or inherent
behavior.
The acquired behavior becomes more variable and modifiable through experience. The
adaptation of the individual organism may develop uniquely in its life history through the
process of learning, such behavior patterns are known as acquired type. This is two types,
learning and reasoning or problem solution.
Stereotyped behavior:
Stereotyped behavior is of three types: (1) Taxes (2) Reflexes (3) Instincts
1. Taxes: Taxes mean the orientation of the body with respect to the source of stimulation. It is a
simple movement influenced by the direction of the stimulus. In taxis, the animal’s body takes
up a particular direction which may be combined with locomotion so that the animal moves
towards, away from or at a fixed angle to the source.
Types of Taxes:
1. Klinotaxis: In this case, animal receptor is not capable of discriminating the source of
stimulation. The animal can compare the intensity of stimulation on the two sides of its body by
turning the receptor in one side and then in the other. This comparison is successive and enables
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
the organism to turn until both sides are stimulated equally. Example: It is seen in the response of
maggots of common flies like Musca sp. to light during the period proceeding pupation.
2. Tropotaxis: In this type of taxis, the comparison of stimulation is simultaneous. It depends on
bilaterally symmetrical receptors arranged in such a way that they are stimulated unequally when
the animal is not oriented towards or away from the source of stimulation. This simultaneous
comparison makes possible orientation towards or away from a localized source without the
lateral swings or wavy movement necessary in klinotaxis. Example: The dorsal light reaction,
shown by many aquatic and areal animals. In this reaction, animals move in a plane of at right
angle to the source of stimulation rather than towards or away from the stimulation.
3. Telotaxis: This type of taxis does not depend on simple balance as in case of klino-and
tropotaxis. If there are two source of stimulation operating through the same modality, animal
orients towards one or other and not in an intermediate direction. Example: Orientation of
dragonfly towards the prey.
4. Menotaxis or light compass response: It involves orientation at constant angle to the
direction of source of stimulation. Example: Light compass reaction of ants and bees.
5. Mnemotaxis: It does not involve configurational stimuli, however, orientation depend on
complex stimulus condition. Example: Insects return is guided by the relation of the nest
entrance to the whole configuration of land marks and does not depend on stimulation of special
parts of retina by particular land marks.
Types of Stimulus Bound Taxes:
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
1. Phototaxis 2. Thermotaxis 3. Chemotaxis 4. Geotaxis 5. Rheotaxis 6. Thigmotaxis 7.
Galvanotaxis
(2) Reflexes
Reflexes are very similar to taxes because they are relatively stereotyped and they fit into the
definition of innate behavior in the sense they are outcome of inherited neural mechanism. There
are two types of reflexes:
1. Tonic reflexes: They are slow, long lasting adjustments which maintain muscular tone, posture
and equilibrium.
2. Phasic reflexes: They are rapid short lived adjustments as seen in the flexure response.
(3) Instincts
Instincts are the more complex and fascinating of the stereotyped or innate behavior. The
instinctive behaviors of organisms are genetically based as the result of natural selection. Genes
are responsible for all the behavioral pattern and these are modified and preserved with natural
selection. Example: Birds songs.
7. What is communication? With suitable example describe the communication in Honey
bee.
In the context of animal behavior communication is the sharing of information between
individuals. Animals convey information to members of their own species and to other species as
well through an incredible diversity of sounds, colours, flashing lights, smells and postures.
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
Communication is the process of transferring information from sender to receiver to the benefit
of the sender, on average. Biological communication is broadly defined as an action on the part
of one organism that alters the probability patterns of behavior in a fashion adaptive to either one
or both of the participants. Animal signal is the physical form in which the transmission from
one to other takes place.
Communication in Honey bee
Group-living animals sometimes communicate the location of food and other resources to one
another. Such communication is well studied in honeybee.
Von Frisch studied the dance language of honeybee and he got Nobel Prize in 1973 for this.
There are two types of dances:
1. Round dance: The round dance is a circling dance, just as the name implies: the bee runs
in a circle, then reverses direction and circle again (Fig-1).
2. Waggle dance: It is in the shape of a figure 8. The bee runs in a straight line through the
center, circles to the right, runs straight through the center again, and then circles to the
left (Fig-2). During the central run, called the “waggle run”, the bee waggles her
abdomen about 15 times per second and buzzes her wings at about 250 beats per second.
Model Answer BSc IV Sem Zoology, Paper II
After several experiment
honeybee performed after finding food near the hive. However, the waggle dance
performed after finding food greater than about 50 m from hive.
odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour
After several experiment, Von Frisch finally suggested that the round dance of a
honeybee performed after finding food near the hive. However, the waggle dance
performed after finding food greater than about 50 m from hive.
Evolution and Animal Behaviour 2013
, Von Frisch finally suggested that the round dance of a
honeybee performed after finding food near the hive. However, the waggle dance
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
8. Describe about parental care in amphibians.
Looking after the eggs or the young until they are independent, to defend the predator, is known
as parental care. The method of caring by Amphibia generally fall under two categories:
(1) Protection by nests, nurseries or shelters
(2) Direct caring by parents
(1) Protection by nests, nurseries or shelters:
1. Selection of site: Many amphibians lay eggs in protected, moist microhabitats on land.
Example: Species of Phyllamedusa, Hylodes etc.
2. Defending eggs or territories: Example: male of green frog Rana clamitans, etc.
3. Direct development: In some terrestrial or tree frogs, such as Eleutherodactylus, Arthrolepit
and Hyla nebulosa, the eggs hatch directly into little frogs thus avoiding larval mortality.
4. Foam nests: Many Amphibians convert copious mucos secretion into nests for their young.
Example: Japanies tree frog Rhacophorus schlegeli.
5. Mud nests: Brazilian tree frog, Hyla fabre
6. Tree nests: Southe American tree frog, Phyllomedusa hypochondrales.
7. Gelatinous bags: In Phrynixalus biroi large eggs are enclosed in a sausage-shaped transparent
gelatinous membranous bag, secreted by female and left in mountain streams.
(2) Direct caring by parents:
Model Answer BSc IV Sem Zoology, Paper II Evolution and Animal Behaviour 2013
1. Coiling around eggs: In congo ell Amphuima and certain caecilians like Ichthyophis and
Hypogeophis.
2. Transferring tadpoles to water: Some species of small frog, (e.g., Phyllobates, Arthroleptis,
Pelobate), transported hatching tadpoles to water with their sucker like mouth.
3. Eggs glued to body: Many amphibians, instead of remaining with the eggs, carry the eggs
glued to their body. Example: In the dusky salamander, Desmognathus fuscus, female carries the
string of eggs coiled around her neck, until they have hatched.
4. Eggs in back pouches: In some group of tree frogs called marsupial frogs or toads, the female
carries the eggs on her back, either in an open oval depression, a closed pouch or in individual
pockets.
5. Organs as brooding pouches: Male of the South American Darwin’s frog, Rhinoderma
darwinii, pushes at least two fertilized egg into his relatively large vocal sacs. Here, they undergo
complete development to emerge out a fully fromed froglets.
6. Viviparity: Some anurans are ovoviviparous. They retain their eggs in the oviducts and the
female give birth to living young. Examples: African toads, Nectophrynoides and Pseudophryne,
the Europian salamander Salmandra salamandra.