Heredity and evolution

Question 1

Question: Which type of reproduction produces identical offspring and which type does not produce offspring that are exactly similar to the parents?
Answer: Asexual reproduction produces identical offspring while sexual reproduction does not produce offspring that are exactly similar to the parents.

Question 2

Question: Why do we see different kinds of organisms around us?
Answer: We see different kinds of organisms around us due to variations.

Question 3

Question: Define heredity. Give some common instances of inherited traits in Humans.
Answer: Heredity may be defined as the transmission of characteristics through generations. Common instances of inherited traits may include, colour of skin, colour of eyes, diseases like, diabities and conditions like baldness

Question 4

Question: Who was Gregor Mendel and what was his contribution to science?
Answer: Gregor Mendel was an Austrian monk who first started the study of inheritance in an organized manner. This was the beginning of genetics and therefore, he is called the Father of Genetics.

Question 5

Question: Which plant did Mendel select for his studies and why?
Answer: Mendel selected the purebred garden pea plant for his studies. These plants showed many contrasting traits that were easy to track through the generations.These plants are naturally self-pollinated allowed him to easily get pure lines for his studies.

Question 6

Question: What are hybrids? How does one distinguish a monohybrid from a dihybrid cross?
Answer: The plants produced as a result of cross between two different plants are called hybrids. Monohybrid cross is the cross between two organisms in which the inheritance of only one trait is followed. The crosses that study two traits together are called the dihybrid crosses.

Question 7

Question: What are phenotype and genotype?
Answer: Phenotype refers to the externally exhibited trait whereas genotype refers to the traits developed by genes.

Question 8

Question: What is the physical basis of heredity? What are alleles?
Answer: Genes are the physical basis of heredity. The different expressions of the same genes are called alleles.

Question 9

Question: What are homozygous and heterozygous plants?
Answer: Homozygous plants are those with similar alleles for a trait. Heterozygous plants have different alleles for a trait.

Question 10

Question: What are the phenotypic and genotypic ratio in the F₂ generation in monohybrid cross?
Answer: The phenotypic ratio in the F₂ generation in monohybrid cross is 3:1 and the genotypic ratio is 1:2:1.

Question 11

Question: Which are the allelic forms of the gene for height?
Answer: The two allelic forms of the gene for height are T, the dominant gene for tallness and t, the recessive gene for dwarfness.

Question 12

Question: What is the law of unit characters?
Answer: According to the law of unit characters, all the traits are separate entities or units by themselves whose inheritance is controlled by factors, now called genes.

Question 13

Question: What occurs during allopatric speciation? Give an example.
Answer: A population splits into two geographically isolated allopatric populations during allopatric speciation. For instance, a species like mice or fruit flies may get isolated if they travel on a ship to a relatively virgin island. New speciation starts because the original and new populations are not in contact anymore and do not interbreed. The original gene pool gets cut off and certain rare genes that may have surfaced in the new population may cause it manifest modified characteristics and ultimately new species.

Question 14

Question: Where are genes present and what are they made up of?

Answer: Genes are present arranged in a linear manner on the chromosomes. They are made up of series of nucleotides in a particular sequence.

Question 15

Question: Which are the two types of chromosomes and what is the difference between them?
Answer: The two types of chromosomes are: autosomes and sex chromosomes. While autosomes have homologous chromosomes as pairs, sex chromosomes are of two different types - X and Y.

Question 16

Question: What do you understand by Morphological change? How are analogous structures in determining species evolution
Answer: morphology involves the study of the external features of organisms. Analogous structures refer to structures that are similar because of the function they carry out and in their external appearance. However, these structures differ internally. Such structures are called analogous structures. Anologues help us distinguish relationships between organismsand functions which are similar but belong to a a different phylogenetic type For example, wings of bat and a bird are similar in appearance and function but they are internally very different and have different origins.

Question 17

Question: Define variation. How variations are classified based on origin?
Answer: Variation may be defined as differences among individuals of a species. Variations are classified as follows based on the origin:

Somatogenic They are somatic and non-inheritable. They are caused by the influence of the environment upon the somatic cells. For example, strong sunlight causes skin to darken in humans.

Blastogenic There are changes that occur in the genes of the organism. These changes may be heritable. The changes may be due to assortment of genes during meiosis in sexual reproduction or due to some sudden change in the composition of genes or chromosome number. An example of change due to meiosis is the difference in height of a population.

Question 18

Question: Which variation contributes to evolution - somatogenic or blastogenic? Why?
Answer: Blastogenic variation contributes to evolution as it is inheritable and passed on from generation to generation.

Question 19

Question: What is speciation? What are it impotrtant attributes? How does it differ from evolution.
Answer: Speciation is the evolutionary process by which new biological species arise. The new species cannot breed with its parent species and interbreeding only takes place between members of the new species. Evolution looks at the gradual development of overall species over a much longer time period and the evolution of more complex species from pre-existing simpler forms. Speciation refers to the development of one or two species.

Question 20

Question: Which are the various fields from which evidences for evolution can be used?
Answer: The various fields from which evidences for evolution can be used are genetics, paleontology, molecular biology, ecology and ethology (study of behaviour).

Question 21

Question: What are petrifactions?
Answer: The skeleton remains for sometime and the sediments harden around it. The soft parts disintegrate and the gaps created in this manner are filled by mineral deposits such as silica, calcium carbonate, etc. Such fossils are called the petrifactions. Finer details are also preserved in such fossils.

Question 22

Question: What are homologous and analogous organs?
Answer: Organs that have common basic form but are present in different species are called the homologous organs. Thus the wings of bat are homologous to the limbs of man. Analogous structures are those that show no similarity in the internal structure or anatomy but appear similar in appearance and function on the outside. Bird and bat wings are analogous-that is, they have separate evolutionary origins, but are superficially similar because they evolved to serve the same function.

Question 23

Question: 'The haemoglobin of chimpanzees differs from that of man in only 1 amino acid, of gorilla in 3 amino acids and of gibbon in 8 amino acids.' What does this statement indicate?
Answer: The statement means that there are only minor differences in the hemoglobin structure of the four primates. It is a reliable indicator pointing to the fact that these four groups are linked.

Question 24

Question: What is a 'phylogenetic' tree?
Answer: Evolutionary change and relationships of related organisms are represented in "family trees," or 'phylogenetic' trees, which show the relationships among organisms to illustrate the idea that all of life is related. The trees will trace evolutionary stages of spices and show at what stage evolutionary paths of species diverge or branch as lineages evolve and split and modifications are inherited. Many of the phylogenies one encounters are the "family trees" of groups of closely related species.

Question 25

Question: What are the evolutionary mechanisms that directly affect gene frequencies in a population? Describe any one of them.
Answer: Micro-evolutionary changes that directly affect gene frequencies in a population can happen in a four basic ways: mutation, migration, genetic drift, and natural selection. Migration refers to some members of the population leaving and going away to different habitats. Conversely, it can refer to new members from ther similar populations joining in.

Question 26

Question: What is the genetic material in most organisms?
Answer: The genetic material is a nucleoprotein called chromatin. It is made up of DNA - a double stranded helical polynucleotide molecule and protein.

Question 27

Question: How are the chromosomes in males different from the chromosomes in females? What determines the sex of a human being?
Answer: In males, the sex chromosomes are heterologous (XY) and in females, the sex chromosomes are homologous (XX). The chromosome inherited from the father determines the sex.

Question 28

Question: What is common to micro evolution and macro evolution?
Answer: While there is a large difference in terms of time scale and level of study micro evolution and macro evolution, the mechanisms that cause evolution i.e., mutation, migration, genetic drift, and natural selection are common to both.

Question 29

Question: What is the importance of the duck billed platypus to evolution.
Answer: The animal is a living fossil that links warm blooded mammals to cold blooded reptiles. It appears to have features of both and does not exactly fit into any phylogentype or group of organisms.

Question 30

Question: The more characteristics two species will have in common, the more closely they are related. Explain.
Answer: Species evolve from their parent species by creating a new gene pool. As this continues in the evolutionary process many types of species will develop in different environments which we cannot imagine as being linked. For instance the whale has more common linkages to hoofed animals like the giraffe! However as we trace the evolution or linr=eage backwards we find, common shared characteristics or traits that places them in the same group. A tree and a dog may not have any characteristic common, but mammals have four limbs, similar to birds, reptiles and amphibians. The basic structure of the limbs is similar though it has been modified to perform different functions in various vertebrates. Such a homologous characteristic helps to identify an evolutionary relationship between apparently different species.. Apes like the orangutan and man have many homologous characteristics which place them close together on the evolutionary ladder.

Question 31

Question: How do we know how old fossils are?
Answer: There are two ways to estimate the age of fossils One is relative. If we dig into the earth, the fossils we find closer to the surface are more recent than the fossils we find in deeper layers. The age of the layers can be seen by the rock formation type. The second way of dating fossils is by detecting the ratios of different isotopes of the same element in the fossil.