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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


odel Answer BSc IV Sem Zoology, Paper II Evolution and Animal BehaviourEvolution and Animal Behaviour 2013


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:


. Describe the evidences of organic evolution from comparative anatomy.


on the same basic plan. The minor differences seen in some forms are the adaptive m

living. This can be discussed under following heads:



on the same basic plan. The minor differences seen in some forms are the adaptive modification


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


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


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


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.


curve of variability for the distribution of measurements of phenotypic traits.


a regular change within a population in one direction in respect to


It is progressive selection which removes more individuals from one end of the normal bell


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.


curve of variability for the distribution of measurements of phenotypic traits. The elimination


a regular change within a population in one direction in respect to


one end of the normal bell-


. The directional selection

nmental change and the gene frequency of a particular gene

The development of resistance to DDT or other insecticide by


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.


Resistance of bacteria to drug or antibiotics: Role of directional selection is demonstrated by

to increasing concentration of drug, chloroamphenicol,


forms have better chances of survival than the nonresistance bacteria.

to break up a previously homogenous population into several



highest fitness and the intermediate or mean values are relatively

Examples: Sunflower population, mimetic butterflies.


ole of directional selection is demonstrated by

to increasing concentration of drug, chloroamphenicol, this raised


previously homogenous population into several



highest fitness and the intermediate or mean values are relatively


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


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.


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:


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.


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


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:


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.


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.


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.


After several experiment, Von Frisch finally suggested that the round dance of a


performed after finding food greater than about 50 m from hive.


, Von Frisch finally suggested that the round dance of a



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:


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.

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