KPK Board 12th Class Biology Ch 24 Evolution Short Questions Answers

the difference of form size colour habits and Physiology it is among the members of same species are known as variation its types continuous variation in this type a lot of intermediate characters can be observed between two extreme of a character they can be modified by environment effect there are more than one gene for a character is the show additive effect skin colour and height.

discontinuous variation in this type no intermediate characters are observed that cannot be modified by environment affect the characters are controlled by few genes and the gene do not show additive effect

The word evolution means change definition it is the change in inherited characters of biological population over successive generation evidences comparative anatomy or organism vestigial organs comparative embryology natural and artificial selection.

Cretinism this theory ovas  for the first time proposed by Aristotle.

statement according to this theory all living things came into existence in their present state specifically created by nature their position on scale nature was considered to be permanent and not changed.

This theory stated several key organelles of eukaryotes originated as Symbiosis between separate single cell organism according to this theory the mitochondria and plastids and possible other organelles represent formerly  free living bacteria that were taken inside another cell.

by the early  1840 Darwin had worked out the major features of theory natural selection as the mechanism of evolution in 1844 he wrote a long essay on the origin of species and natural selection.

important points important points of Darwin’s theory are over production struggle for existence variation speciation natural selection are survival of fittest.

the competition in organisms are termed by Darwin as struggle for existence the struggle for existence maybe three fold in nature intraspecific It is a competition between the members of same species inter specific it is the competition between members of different species extra space are the struggle against the forces of nature.

survival in the struggle for existence is not random but depend on hereditary constitution of the surviving individuals the individuals who inherited characters fit them best to their environment are likely to leave more offsprings than less fit individuals that leave less  characters fit them best to their environment are likely to leave more offsprings than less fit individuals that leave less fit offspring this is the best fit offSprings are selected by nature to survive this is known as survival for the fittest Are natural selection.

progress in population Genetics in 1930 mendelism and darwinism were recognised and the genetic basis of variation and natural selection was worked out does a comprehensive theory of evolution was developed 1940 known as modern  synthesized and new darwinism.

it is also known as sensor size because it integrated discoveries and ideas from many different fields including paleontology taxonomy biogeography and population genetics.

it is also known as hybridization barriers these are the collection of mechanism that are prevent the members of different species to produce fertile offspring these mechanisms maintain the integrity of asepsis and in the establishment of new species for bringing about evolution.

studies of comparative anatomy provide many evidence of evolution  homology in forelimbs the same skeletal elements makeup the forelimbs of human whales cats bats and all other mammals Arma- man

Wings- bat

flippers- whale

fore legs- cats

it indicate the common Anatomical them that had been modified for divergent functions.

the succession of fossil from strong evidence in favour of evolution the oldest known fossils are the prokaryotes example for sale horses represent such a series that lead from an ancient primitive for several intermediate stages and end in modern form giraffe elephants and several mollusics show a gradual evolution of body from overtime another example is archaeopteryx the Fossil bird discovered from rocks in East Germany that posses both reptilian and  Avian characters.

the organs that  reduce or may  even lose   its function is known as vestigial organs.

functions it is believed that vestigial organs were once functionable in the ancestors it is the most convincing evidence of evolution examples nictitating membrane Appendix in carnivorous and man coccyx tailbone in men legs bones in snake 

closely related organisms Go through similarly in their embryonic development.

At embryonic development similarities between fish, frog snakes, birds and humans are more Apparent all multicellular animals begin their life as unicellular fertilized egg during embryonic development and all organisms repeat their ancestral  history. Comparative embryology can often establish Homology among structure such as Gill pouch that become so   altered in later development that their common origin would not be apparent by comparing their fully developed forms.

divergence evolution it is the population of differences between groups which can lead to the formation of new species Limbs of vertebrates convergence evolution it describes the similar features it creates similarly formed or functioning analogous structures Lacked by the groups

Last common ancaster wings of bats, insects and birds.

(p2+2pq+q2)

Where,           p = (A) +½ AG

q= (a) +½(A)

P+q = 1

p=1-q

(p+q)2 = 1

P2+2pq+q2 = 1

genetic drift is the change in the frequency of variation in a population due to random sampling these alleles in offsprings are a sample of those in the parents and chance has a role in determining whether a given individual survive and reproduce when there are few copies of an allele the genetic drift is largest and when there are many copies the effect is smaller.

speciation is the evolutionary process by which new biological species arise the term was for the first time used by biologist  Orator . F . Cook.

specialisation is caused by different factors including random fertilization crossing over natural selection.

It refers to the formation of two are more  descendant species from a single ancestral species all occupying the same geographical location it is most commonly observed in insects that become dependent on different host plants in this types the group of offsprings will be produced with twice number of the chromosome it is rare speciation and is more common in plant.

it is the most common form of population it occurs when the population of a species become geographically isolated for gene flow in population cases the population may become different in response to the natural selection imposed by their different environment the population may have different allele frequencies when they were separated. 

it occurs very rarely when populations are separated not by geographical barriers when but by Extreme change in in habitat these populations may interbreed they often developed distinct characteristics and lifestyle .