A. If both A and R are true and R is correct explanation for A

D. If both A and R are false.

(a) A and R are true, R is the correct explanation of A

Offsprings produced by asexual reproduction are called clones, because they are genetically as well as morphologically similar to the parent organism.
They are not only similar to one another, but are also exact copies of their parent (e,g): Amoeba, Spirogyra, Hydra, Yeast, etc.

Haplodiploidy is a sex determination system in which males develop from unfertilized eggs are haploid, and female develops from fertilized egg and is diploid.
It is sometimes called arrhenotoky.
e.g., Honeybees, ants, and wasps.

The inactivation of an X chromosome one of the two X chromosomes in every cell in some female mammal is randomly inactivated early in embryonic development and named after geneticist Mary Lyon.
The inactive X chromosome is silenced by it being packaged in such a way that it has a transcriptionally inactive structure called heterochromatin found in nucleoplasm of nucleus.

1. The genetic code is universal. It means that all known living systems use nucleic acids and the same three base codons (triplet codon) direct the synthesis of protein from amino acids. E.g, mRNA ,(UUU) codon codes for phenylalanine in all cells of all organisms.
2. Some exceptions are reported in prokaryotic, mitochondrial and chloroplast genomes. However similarities are more common than differences.

There are 1.4 million locations where single base DNA differences (Called SNPs - Single Nucleotide Polymorphism - pronounce as snips) occurs in human's genome.
(i) By tracing human history
(ii) By finding chromosomal locations for disease associated sequences

(a) ZIFT - Zygote Intra Fallopian Transfer
(b) ICSI - Intra Cytoplasmic Sperm Injection

Mary Lyon suggested that Barr bodies represented an inactive chromosome, which in females becomes tightly coiled into a heterochromatin, a condensed and visible form of chromatin. The number of Barr bodies observed in cell was one less than the number of X-Chromosome. XO females have no Barr body, whereas XXY males have one Barr body.

The fusion of morphological and physiological identical gatnetes (isogametes) is called isogamy. E.g. Monocystis

In plasmodium multiple fission occurs in the schizont and oocyte stages.

Rubella Virus - causes Measles
Polio virus - causes Poliomyelitis

The uterus or womb is a hollow, thick-walled, muscular, highly vascular and inverted pear shaped structure lying in the pelvic cavity between the urinary bladder and rectum.

In some aquatic environments, an inverse relationship between water temperature and fish meristic characters is observed - lower the temperature, more the vertebrae.

Streptokinase produced by the bacterium Streptococcus and genetically engineered Streptococci are used as "clot buster" for removing clots from the blood vessels of patients who have undergone myocardial infarction.

(i) Tubectomy is the surgical sterilisation method in women.
(ii) Vasectomy is the surgical sterilisation method in male.

Stabilizing selection
Directional selection
Disruptive selection

1) Janani Suraksha Yojana
2) Shishu Suraksha Karyakaram
3) RMNCH+A Programme
4) Pradhan Mantri Surakshit Matritva Abhiyan

(a) Insemination: Transfer of sperms by the male into the female genital tract.
(b) Fertilization: Fusion of male and female gametes to form a zygote, called fertilization

Trisomic condition of chromosome - 21 results in Down's syndrome. It is characterized by severe mental retardation, defective development of the central nervous system, increased separation between the eyes, flattened nose, ears are malformed, mouth is constantly open and the tongue protrudes.

After infection of RBC with sporozoite, when the RBC ruptures a toxic substance haemozoin is released which causes shivering chills and high fever followed by sweating

Interferons are used for the treatment of various diseases like cancer, AIDS, multiple sclerosis, hepatitis C and herpes zoster

Totipotency is the ability of a single cell to divide and produce all of the differentiated cells in an organism.
Unipotency refers to the ability of the stem cells to differentiate into only one cell type

(a) Himalayas
(b) Indian deserts
(c) Trans-Himalayan region
(d) Western ghats.

(a) George, the tree snail (Achatinella apexfulva)
(b) Sudan - Northern white rhinoceros (Ceratotheriurri simum)

Alexander Flemming discovered the first antibiotic from the fungus Penicillium no Tatum and Pencillium Chrysogenum

In eukaryotes, the promoter has AT rich regions called TATA box or Goldberg-Rogness box. It acts as a binding site for RNA polymerase.

When run-off from land containing nutrients reaches water bodies like lakes, it results in dense growth of plant life. This phenomenon is called Eutrophication.

Fog

The largest and most nearly self-sufficient biological system is often designated as the Ecosphere, which includes all the living organisms of the Earth, interacting with the physical environment to regulate their distribution, abundance, production and evolution

Tetracycline inhibits binding between aminoacyl tRNA and mRNA.
Streptomycin inhibits initiation of translation and causes misreading.

Homo sapiens or modem human arose in Africa some 25,000 years ago and moved to other continents and developed into distinct races. They had a brain capacity of 1300 - 1600 cc. They started cultivating crops and domesticating animals.

Heterogametic Males:
In this method of sex determination the males are heterogametic producing dissimilar gametes while females are homogametic producing similar gametes.
It is of kinds XX-XO type and XX-XY type.
(i) XX-XO Type
(a) This method of sex determination is seen in bugs and some insects such as cockroaches and grasshoppers.
(b) The female with two X chromosomes are homogametic (XX) while the males with only one X chromosome are heterogametic (XO).
(c) The presence of an unpaired X chromosomes determines the male sex. The males with unpaired 'X' chromosome produce two types of sperms, one half with X chromosome and other half without X chromosome.
(d) The sex of the offspring depends upon the sperm that fertilizes the egg.
 
(ii) XX-XV type (Lygaeu Type):
This method of sex determination is seen in human beings and in Drosophila.
(a) The females are homogametic with XX chromosome, while the males are heterogametic with X and Y chromosome.
(b) Homogametic females produce only one kind of egg, each with one X chromosome, while the heterogametic males produce two kinds of sperms some with X chromosome and some with Y chromosome.
(c) The sex of the embryo depends on the fertilizing sperm. An egg fertilized by an 'X' bearing sperm produces a female, if fertilized by a 'Y' bearing sperm, a male is produced.

1. Natural selection can be explained clearly through Industrial melanism.
2. Industrial melanism is classical case of natural selection exhibited by the peppered moth.
Biston Betularia
1. These were available in two colours, white and black. Before industrialization peppered moth both white and black coloured were common in England (Manchester).
2. Pre-industrialization witnessed white coloured background of the wall of buildings hence the white coloured moths escaped from their predators.
3. Post Industrialization the tree trunks become dark due to smoke and soot let out from the lndustries.
4. The black moths camouflaged on the dark bark of the trees and the white moths were easily identified by their predators (birds).
5. Hence the dark coloured moth population was selected and their number increased when compared to the white moths nature offered positive selection pressure to the black coloured moths.
6. The above proof shows that in a population organisms that can adapt will service and produce more progenies resulting in increase in population through natural selection.

1. A patient is suffering from ADA deficiency can be caused by using "gene therapy''.
2. Gene therapy is a correction of a genetic defect that has been diagnosed in a child embryo.
3. ADA enzyme is crucial fol the immune system to function.
4. Deletion of the gene for adenosine deaminase results into ADA deficiency.
5. In some children, ADA deficiency can be cured by bone. Marrow transplantation While in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches is that they are not completely curative.
6. It may recurrent in nature as in the process of gene therapy, Lymphocytes used are found not to be immortal in nature and the patient requires a periodic infusion of such genetically engineered lymphocytes.
7. For permanent cure, gene isolated from the bone-marrow-cells producing ADA is introduced into cells at early embryonic stages.

The methods adopted for the improvement of human beings are
(i) Eugenics
(ii) Euthenics
(iii) Euphenics
Eugenics:
Application of the laws of genetics for the improvement of human race is called eugenics. The term eugenics means "well born" and was coined by Francis Galton in 1885. For the betterment of future generations it is necessary to increase the population of outstanding people and to decrease the population of abnormal and defective people by applying the principles of eugenics.
Two methods of Eugenics
(i) Constructive method or Positive eugenics
(ii) Restrictive method or Negative eugenics
(i) Positive eugenics: Positive eugenics attempts to increase consistently better or desirable germplasm and to preserve the best germplasm of the society. The desirable traits can be increased by adopting the following measures:
a) Early marriage of those having desirable traits
b) Subsiding the fit and establishing sperm and egg banks of precious germplasm 
c) Educating the basic principles of genetics and eugenics
d) Improvement of environmental conditions
e) Promotion of genetic research
(ii) Negative eugenics: Negative Eugenics attempts to eliminate the defective germplasm of the society by adopting the following measures:
(a) Sexual separation of the defectives
(b) Sterilization of the defectives
(c) Control of immigration and
(d) Regulation of marriages
Euphenics:
man is called Euphenics or Medical engineering. In 1960, Joshua Lederberg coined the term Euphenics. It means normal appearing. It deals with the control of several inherited human diseases especially the inborn errors of metabolism. Eg. Phenylketonuria (PKU)
Euthenics:
The science of improvement of existing human race by improving the environmental conditions is called euthenics. It can be achieved by subjecting them to better nutrition, better unpolluted ecological conditions, better education and sufficient medical facilities

In binary fission, the parent organism divides into two halves and each half forms a daughter individual. The nucleus divides first amitotically or mitotically (karyokinesis), followed by the division of the cytoplasm (cytokinesis). The resultant offsprings are genetically identical to the parent. Depending on the plane of fission, binary fission is of the following types
(i) Simple irregular binary fission
(ii) Transverse binary fission
(iii) Longitudinal binary fission
(iv) Oblique binary fission
(i) Simple irregular binary fission is seen in Amoeba like irregular shaped organisms, where the plane of division is hard to observe. The contractile vacuoles cease to function and disappear. The nucleoli disintegrate and the nucleus divides mitotically. The cell then constricts in the middle, so the cytoplasm divides and forms two daughter cells.

(ii) In Transverse binary fission, the plane of the division runs along the transverse axis of the individual. E.g. Paramecium and Planaria. In Paramecium the macronucleus divides by amitosis and the micronucleus divides by mitosis.

(iii) In Longitudinal binary fission the nucleus and the cytoplasm divides in the longitudinal axis of the organism. In flagellates, the flagellum is retained usually by one daughter cell. The basal granule is divided into two and the new basal granule forms a flagellum in the other daughter individual. E.g. Vorticella and Euglena.
(iv) In Oblique binary fission the plane of division is oblique. It is seen in dinoflagellates. E.g. Ceratium.

(i) Plasmodium vivax is a digenic parasite, involving two hosts, man as the secondary host and female Anopheles mosquito as the primary host. The life cycle of Plasmodium involves three phases namely schizogony, gamogony and sporogony (f.g)
(ii) The parasite first enters the human blood stream through the bite of an infected female Anopheles mosquito. As it feeds, the mosquito injects the saliva containing the sporozites.
(iii) The sporozoites within the blood stream enter the hepatic cells of the liver and undergoes multiple asexual fission (schizogony). This produces merozoites which are released from liver cells.
(iv) The merozoites penetrate the RBC's. Inside the RBC of Blood, the merozoite of Plasmodium to develop as unicellular trophozoites. The trophozoite grows in size and a central vacuole develops pushing them to one side of cytoplasm and becomes the signet ring stage.
(v)The trophozoite nucleus then divides asexually to produce the The schizont divides and produces on nucleated merozoites.
(vi) Eventually the erythrocyte lyses, releasing the merozoites and haemozoin toxin into the blood stream to infect other erythrocytes. Lysis of red blood cells results in cycles of fever and other symptoms. This erythrocytic stage is cyclic and repeats itself approximately every 48 to72 or longer depending on the species of Plasmodium involved. The sudden release of merozoites triggers an attack on the RBCs.
(vii) Occasionally, merozoites differentiate into macrogametocytes and microgametocytes When these are ingested by a mosquito, they develop into male and female gametes respectively
In the mosquito's gut, the infected erythrocytes lyse and male and female gametes fertilize to form a diploid zygote called ookinete. The ookinete migrates to the mosquito's gut wall and develops into an oocyte.
The oocyte undergoes meiosis by a process called sporogony to form sporozoites. These sporozoites migrate to the salivary glands of the mosquito. The cycle is now completed and when the mosquito bites another human host, the sporozoites are injected and the cycle begins a new.
The pathological changes caused by malaria, affect not only the erythrocytes but also the spleen and other visceral organs. Incubation period of malaria is about 12 days. The early symptoms of malaria are headache, nausea and muscular pain. The classic symptoms first develop with the synchronized release of merozoites, hemozoin toxin and erythrocyte debris into the bloodstream resulting in malarial paroxysms - shivering chills, high fever followed by sweating. Fever and chills are caused partly by malarial toxins that induce macrophages to release tumor necrosis factor (TNF-a) and interleukin.

A collection of procedures, which includes the handling of gametes and/or embryos outside the body to achieve a pregnancy as known as Assisted Reproductive Technology. It increases the chance of pregnancy in infertile couples. ART includes intra-uterin insemination (IUI), in vitro fertilization, (IVF) Embryo transfer, (ET), Zygote intra-fallopian transfer (ZIPT), Gamete intrafallopian transfer (GIFT), Intra-cytoplasmic, sperm Injection (ICSI), .Preimplantation genetic diagnosis, oocyte and sperm donation and surrogacy.
(i) Intra-cytoplasmic sperm injection (ICSI): In this method only one sperm is injected into the focal point of the egg to fertilize. The sperm is carefully injected into the cytoplasm of the egg. Fertilization , occurs in 75 - 85% of eggs injected with the sperms. The zrgote is allowed to divide to form an 8 celled blastomere and then transferred to the uterus to develop a productive pregnancy.
(ii) Surrogacy: Surrogacy is a method of assisted reproduction or agreement whereby a woman agrees to carry a Pregnancy for another person, who will become the newborn child's parent after birth. Through in vitro fertilization (IVF), embryesz are created in a lab and are transferred into the surrogate mother's uterus.

Species is considered extinct when none of its members are alive anywhere in the world. If individuals of a species remain alive only in captivity or other human controlled conditions, the species is said to be extinct in the wild. In both of these situations, the species would be considered globally extinct. A species in considered to be locally extinct when it is no longer found in an area it once inhabited but is still found elsewhere in the wild.
Types of extinctions:
(i) Natural extinction is a slow process of replacement of existing species with better adapted species due to changes in environmental conditions, evolutionary changes, predators and diseases. A small population can get extinct sooner than the large population due to inbreeding depression (less adaptivity and variation).
(ii) Mass extinction: The earth has experienced quite a few mass extinctions due to environmental catastrophes. A mass extinction occurred about 225 million years ago during the Permian, where 90% of shallow water marine invertebrates disappeared.
(iii) Anthropogenic extinctions: These are abetted by human activities like hunting, habitat destruction, over exploitation, urbanization and industrialization. Some examples of extinctions are Dodo of Mauritius and Steller's sea cow of Russia. Amphibians seem to be at higher risk of extinction because of habitat destruction.

(i) Ovaries are the primary female sex organ producing eggs (ovum).
(ii) They are located one on each side of lower abdomen (pelvis).
(iii) The ovary is attached in pelvic wall uterus by an ovarian ligament called mesovarium.
(iv) It is an elliptical structure of 2-4 cm long
(v) Each ovary is covered by thin cuboidal germinal epithelium encloses ovarian stroma.
(vi) Below germinal epithelium is a dense connective tissue called tunica albuginea.
(vii) The stroma is differentiated into an outer cortex and an inner medulla.
(viii) The cortex is dense and granular due to follicular cells at varying development stages.
(ix) The medulla is a loose connective tissue with blood vessels, lymph vessels and nerve fibres.

Stem cells are undifferentiated cells found in most of the multi cellular animals. These cells maintain their undifferentiated state even after undergoing numerous mitotic divisions. Stem cell research has the potential to revolutionize the future of medicine with the ability to regenerate damaged and diseased organs. Stem cells are capable of self renewal and exhibit 'cellular potency'. Stem cells can differentiate into all types of cells that are derived from any of the three germ layers ectoderm, endoderm and mesoderm.
In mammals there are two main types of stem cells - embryonic stem cells (ES cells) and adult stem cells. ES cells are pluripotent and can produce the three primary germ layers ectoderm, mesoderm and endoderm. Embryonic stem cells are multipotent stem cells that can differentiate into a number of types of cells. ES cells are isolated from the epiblast tissue of the inner cell mass of a blastocyst. When stimulated ES can develop into more than 200 cells types of the adult body. ES cells are immortal ie. they can proliferate in a sterile culture medium and maintain their undifferentiated state. Adult stem cells are found in various tissues of children as well as adults. An adult stem cell or somatic stem cell can divide and create another cell similar to it. Most of the adult stem cells are multipotent and can act as a repair system of the body, replenishing adult tissues. The red bone marrow is a rich source of adult stem cells.
The most important and potential application of human stem cells is the generation of cells and tissues that could be used for cell based therapies. Human stem cells could be used to test new drugs.

Biogas is a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural wastes, manure, municipal wastes, plant material, sewage, food waste, etc., Biogas is produced under the anaerobic condition when the organic materials are converted through microbiological reactions into gas and organic fertilizer. Biogas primarily consists of methane (63 percent), along with CO₂ and hydrogen. Methane-producing bacteria are called methanogens and one such common bacterium is Methanobacterium. Biogas is devoid of smell and bums with a blue flame without smoke. The Methanogens are also present in anaerobic sludge and rumen of cattle. In the rumen, these bacteria help in the breakdown of cellulose. The excreta of cattle called dung is commonly called "Gobar". Gobar gas is generated by the anaerobic decomposition of cattle dung. It consists of methane, CO₂ with some hydrogen, nitrogen and other gases in trace amounts.
In a biogas plant, anaerobic digestion is carried out in an airtight cylindrical tank known as digester. It is made up of concrete bricks and cement or steel. Bio-wastes are collected and a slurry of dung is fed into this digester. It has a side opening into which organic materials for digestion are incorporated for microbial activity. Anaerobic digestion is accomplished in three stages: solubilisation, acidogenesis, and methanogens. The outlet is connected to a pipe to supply biogas. The slurry is drained through another outlet and is used as fertilizer. Biogas is used for cooking and lighting. The technology of biogas production was developed in India mainly due to the efforts of the Indian Agricultural Research Institute (IARl) and Khadi and Village Industries Commission (KVIC).

Radioactive waste management involves the treatment, storage, and disposal of liquid, airborne, and solid effluents from the nuclear industry. Methods of disposal of radioactive wastes are:
1. Limit generation - Limiting the generation of waste is the first and most important consideration in managing radioactive wastes.
2. Dilute and disperse - For wastes having low radioactivity, dilution and dispersion are adopted.
3. Delay and decay - Delay and decay is frequently an important strategy because much of the radioactivity in nuclear reactors and accelerators is very short lived.
4. Concentrate and confine process - Concentrating and containing is the objective of treatment activities for longer-lived radioactivity. The waste is contained in corrosion resistant containers and transported to disposal sites. Leaching of heavy metals and radionuclides from these sites is a problem of growing concern.

The two most characteristic forms of behavioral adaptations are migration and courtship. Migration allows the animals to find better resources or evade threat. Courtship is a set of behavioral patterns to find a mate to reproduce. Most nocturnal animals remain underground or inactive during the daytime. This is a modification of their feeding and activity pattern or habit or behavior.

In eukaryotes, organization is more complex. Chromatin is formed by a series of repeating units called nucleosomes. Kornberg proposed a model for the nucleosome, in which 2 molecules of the four histone proteins H2A, H2B, H3 and H4 are organized to form a unit of eight molecules called histone octamere. The negatively charged DNA is wrapped around the positively charged histone octamere to form a structure called nucleosome. A typical nucleosome contains 200 bp of DNA helix. The histone octameres are in close contact and DNA is coiled on the outside of nucleosome. Neighbouring nucleosomes are connected by linker DNA (HI) that is exposed to enzymes. The DNA makes two complete turns around the histone octameres and the two turns are sealed off by an HI molecule. Chromatin lacking HI has a beads-on-a-string appearance in which DNA enters and leaves the nucleosomes at random places. HI of one nucleosome can interact with HI of the neighbouring nucleosomes resulting in the further folding of the fibre. The chromatin fiber in interphase nuclei and mitotic chromosomes have a diameter that vary between 200-300 nm and represents inactive chromatin. 30 nm fibre arises from the folding of nucleosome, chains into a solenoid structure having six nucleosomes per turn. This structure is stabilized by interaction between different HI molecules. DNA is a solenoid and packed about 40 folds. The hierarchical nature of chromosome structure is illustrated. Additional set of proteins are required for packing of chromatin at higher level and are referred to as non-histone chromosomal proteins (NHC). In a typical nucleus, some regions of chromatin are loosely packed (lightly stained) and are referred to as euchromatin. The chromatin that is tightly packed (stained darkly) is called heterochromatin. Euchromatin is transcriptionally active and heterochromatin is transcriptionally inactive.

1. Polyspermy: An egg that has been fertilized by more than one sperm
2. When a sperm comes in contact with the zona pellucida layer of the ovum, it induces changes in the membrane of the ovum to block the entry of additional sperms.
3. The prevention of polyspermy ensures that only one sperm can fertilize a single ovum.

1. Testes are the primary male sex organs.
2. They are a pair of ovoid bodies lying in the scrotum.
3. The scrotum is a sac of skin that hangs outside the abdominal cavity.
4. Since viable sperms cannot be produced at normal body temperature, the scrotum is placed outside the abdominal cavity to provide a temperature 2-3°C lower than the normal internal body temperature.
5. Thus, the scrotum acts as a thermoregulator for spermatogenesis.

Structural gene	Regulatory gene	operator gene
They are concerned with the transcription of mRNA for the synthesis of particular polypeptide	It controls the functioning of operator gene	It determines the functioning of operator gene
They function only when RNA polymerases join	It produces a repressor or apo- repressor for blocking operator gene	It works only when it is not blocked by repressor
They function by forming mRNA for specific polypeptide	It functions through the formation of mRNA of repressor or apo-repressor	It functions through the presence (or) absence of repressor

The term biodiversity was introduced by Walter Rosen (1986). Biodiversity is the assemblage of different life forms. Each species is adapted to live in its specific environments.
The changes in climatic conditions are reflected in the distribution and pattern of biodiversity on our planet. The number of species per unit area declines as we move from tropics towards the poles. The Tundra and Taiga of northern Canada, Alaska, northern Europe and Russia possess less than 12 species of trees. The temperate forests of the United states have 20-35 species of trees, while the tropical forests of Panama have over 110 species of trees in a relatively small area.

Affected individuals lack the tyrosinase enzyme which converts DOPA to melanin pigment responsible for skin colour. It is caused due to autosomal recessive genes

(I) The third base of the codon is called wobble base and this portion is called wobble position. The actual base pairing between codon of mRNA and anticodon of tRNA occurs at first two positions only. The pairing at the third base need not be complementary. This is called Wobbling.
(II) It allows more than one tRNA to code for an amino acid.

Statins : produced by the yeast Monascus purpureus have been used to lower blood cholesterol levels. It acts by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

S.No	National parks in Tamil Nadu	Districts(s)
i.	Indira Gandhi (Annamalai) NP	Coimbatore
ii.	Mudumalai NP	Nilgiris
iii.	MukurthiNP	Nilgiris

(a) Arrhenotoky: In this type, only males are produced by parthenogenesis. eg: honey bees
(b) Thelytoky: In this type of parthenogenesis only females are produced by parthenogenesis. e.g: Solenobia
(c) Amphitoky: In this type parthenogenetic egg may develop into individuals of any sex. e.g: Aphis.

LNG-20 is an Intra Uterine System of contraceptive method. It increases the viscosity of cervical mucus and thereby preventing the sperms from entering the cervix.

Menstrual hygiene is vital for good health, well-being, dignity, empowerment, and productivity of women. The impact of poor menstrual hygiene on girls is increased stress levels, fear and embarrassment during menstruation. This can keep girls inactive during such periods leading to absenteeism from school.

ELISA is highly sensitive and can detect antigen even in nanograms.
ELISA test does not require radio isotopes or radiation counting apparatus

Cholera, Anthrax, and Rabies

The Bishnois, who are known conservators of their forest, were inspiration to many people's participatory movements for Environmental protection in India. The Chipko movement resisted the destruction of forests of India in the 1970s. Sunderlal Bahuguna was the leader of this movement. People in the movement hugged the trees, and prevented felling of trees by contractors.

Higher the altitude, lower the atmospheric oxygen. Hence to compensate the oxygen demand they adapt themselves showing enhanced RBC count in the blood.

Coprolites are the hardened faecal matters occurs as small pieces. Analysing the coprolites helps to understand the nature of diet of pre-historic animals.