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(b) all finches of islands subjected to adaptive radiation

(c) germ theory of disease

(a) analogous

Epiglottis is not a vestigial structure in Homo sapiens

It is considered as a connecting link between reptilia and aves.

(b) analogous organ

Factors Affecting Hardy–Weinberg Equilibrium 

i. Gene migration or gene flow: When individuals migrate to another place or population, new genes or alleles are added to new population and are lost from old population, in turn changing the frequencies. When gene migration occurs many times, it is called gene flow. 

ii. Genetic drift: Changes occurring in frequencies by chance is called genetic drift. Sometimes, due to changes in allele frequency in new population, some form a different species. This effect is called founder effect and the original drifted population is called founder. 

iii. Mutation: Advantageous mutations lead to new phenotypes and over few generations, result in speciation. 

iv. Genetic recombination: During gametogenesis, variations due to recombination result in new phenotypes. 

v. Natural selection: Heritable variations that enable survival of the fittest will leave greater number of progeny. Natural selection can have following three effects: 

a. Stabilisation: Larger number of individuals acquire mean character value so peak gets higher and narrower. 

b. Directional change: Large number of individuals acquire value other than mean character value so peak shifts in one direction. c. Disruption: Large number of individuals acquire peripheral character values at both ends of the distribution curve and hence 2 peaks are formed.

Natural selection occurs when one allele (or combination of alleles of differences) makes an organism more or less fit to survive and reproduce in a given environment. If an allele reduces fitness, its frequencies tend to drop from one generation to the next. 

The evolutionary path of a given gene (i.e) how its allele’s change in frequency in the population across generation, may result from several evolutionary mechanisms acting at once. For example, one gene’s allele frequencies might be modified by both gene flow and genetic drift, for another gene, mutation may produce a new allele, that is favoured by natural selection

Genetic drift / Sewall Wright Effect is a mechanism of evolution in which allele frequencies of a population change over generation due to chance (sampling error). Genetic drift occurs in all population sizes, but its effects are strong in a small population. It may result in a loss of some alleles (including beneficial ones) and fixation of other alleles.

Genetic drift can have major effects, when the population is reduced in size by natural disaster due to bottle neck effect or when a small group of population splits from the main population to form a new colony due to founder’s effect.

Although mutation is the original source of all genetic variation, mutation rate for most organisms is low. Hence new mutations on an allele frequencies from one generation to the next is usually not large.

According to Hardy–Weinberg, the disturbance in genetic equilibrium is the result of evolution.

As per Hardy Weinberg, change of frequency of alleles in a population would be considered as evolution i.e. distubance in the genetic equilibrium.

(a) Hardy-Weinberg principle 

(b) gene flow and genetic drift

(c) they become a different species

The fittest are not necessarily the strongest individuals , but those individuals who are the bearers of advantageous inherited traits that allow them to survive and reproduce more than others natural selection.

a. He could not get desired results because: 

i. O₂ was used instead of H₂. 

ii. Temperature maintained was 80°C instead of 800°C. 

b. It was concluded that life could have come from pre-existing non-living organic molecules and their formation was preceded by chemical evolution. 

c. Urey and Miller observed formation of amino acids when in a closed flask CH₄, H₂, NH₃ and water vapour were heated at 800°C in presence of electric discharge. Analysis of meteorite content also reveals similar compounds indicating that similar process are occurring elsewhere in space (Chemical evolution). Urey and Miller proved that life originated abiogenetically whereas theory of spontaneous generation emphasised that units of life called spores were transferred to different planets including Earth.

Five factors are

• gene migration or gene flow 
• genetic drift
• Mutation
• genetic recombination
• Natural selection

Hardy-Weinberg principle says that allele frequencies in a population are stable and constant from generation to generation. 

The gene pool remains constant, which is called genetic equillibrium. Disturbance in this equillibrium, ie. change of frequency of alleles in a population results in evolution.

(a) Adaptive radiation 

(b) A number of marsupials, each different from the other evolved from an ancestral stock, but all within the Australian island continent. When more than one adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats), it represents convergent evolution. 

(c) Darwin’s finches represent one of the best examples of this phenomenon. From the original seed-eating features, many other forms with altered beaks arose, it helps them to become insectivorous and vegetarian finches.

Every time we use antibiotics er are applying selection pressure killing off any non-resistant bacteria , thereby, we are actually helping to speed the evolution of resistace to antibiotics.

1. Australopithecus

2. Homo habilus

3. Neanderthal man

4. Java man

5. Cro-magnon man 

6. Dryopithecus

Allele frequencies in a population are stable and constant from generation to generation. (p2+2pq+q2 =1), p, q are individual frequencies of alleles.

The factors are gene migration, genetic drift, mutation, genetic recombination, and natural selection.

1. a – electrodes

b- mixture of gases (CH₄, NH₃, H₂, H₂O)

c – cold water

d – vacuum pump

2. Organic evolution (chemical evolution)

3. (ii) Ammonia, amino acids, proteins, nucleic acids.

1. Adaptive radiation

2. Showed variety in beak structure based on food habits – from seed eating to insectivorous, vegetarian, etc.

3. Australian Marsupials.

Darwin explained that all the verities evolved on the island itself from the original seed-eating birds, many other forms with altered beaks arose some others became insectivorous while remained the vegetarian flinches. Such process of evolution of different species in a given geographied area, starting from a point and literally radiating to other habitats, is called adaptive radiation.

Study of fossils is called paleontology. 

The fossils throw light on past life in following ways: 

i. Distribution of fossil gives information about habitat of an organism. 

ii. Establishes phylogenetic links. 

iii. Some fossils provide evidence of connecting link. 

iv. Age of the organisms can be determined by fossils. 

v. Fossils also throw light on morphology and anatomy of past life.

Exine, the outermost hard layer is chemically composed of sporopollenin, which is highly resistant to high temperature, strong acids, alkali and enzymes.