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 Form 4 Biology questions and answers on evolution

Discuss the various evidences, which show that evolution has taken place.

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Answer Text:
a. Fossils record- Fossils are preserved remains of ancestral forms of organisms that lived long time ago mainly formed from preserved hard parts found on sedimentary rocks. When fossils of
related organism are arranged in chronological order which is made possible by carbon dating, they form fossils record which reveals trends in evolution overtime in the organism concerned e.g humans. This gives direct evidence of the type of organism that existed at a certain geological age.
b. Geographical distribution of organisms- The theory of continental drift supposes that at some time the present day continents were one single landmass which later broke up into parts which drifted apart. Closely related organisms were separated and isolated from one another thus
evolving differently, with time leading to formation of different species through natural selection. Each group of organisms adapted to different set of environmental conditions e.g camels in Africa and illama in South America.
c. Comparative embryology- embryology is the study of formation
and development of an embryo while comparative embryology is a study comparing formation and development of different embryos of all vertebrate show great resemblance and almost impossible to tell them apart. This indicates a common ancestry.
d. Comparative anatomy – Anatomy is the study of structures of living organism. Comparative anatomy is comparison of internal structures of various organisms. Some show basic structural similarities and this suggests that the organisms have a common or related
ancestry e.g homologous structures, but are modified to perform different functions. They have gone through divergent evolution. Example of homologous structures are beaks of birds, feet of birds, pentadtyl limb in mammals. Other structure show basic structural
difference since they have different embryonic origin but have gone through convergent evolution and modified to perform similar function. This are analogous structures e.g wings of bats, insects and birds. Others are vestigial structures –those structures in course of time become greatly
reduced and become functional less. This indicate that they were present in their ancestral forms which have since evolved e.g Coccyx-tails in human, body hair, reduced wings in flightless birds like kiwi.
e. Comparative serology- Serology is the study of blood/serum proteins.
Comparative serology is comparison of different blood proteins in different organisms. This study shows that organisms that are closely related or have common ancestry have similar blood proteins which is tested using antigen –antibody reaction. Where precipitate forms varies
from one animal to another. Greater amount of precipitate shows many common antigen hence common antibodies hence more reaction. This indicates that organisms have a common ancestry. Less amount of precipitate shows that few or none antigen is common in organisms hence are far
apart i.e no common ancestry
f. Cell biology- is the study of cells making up living organisms. Similarities in structures and function of cells point to a common ancestry. The differences that occur between plant and animals cells show that they separated and
evolved differently hence difference that exist among them though they have some organelles that are common


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