a) i) Define the term organic evolution. (2mks) ii) Distinguish between homologous and analogous structures. (2mks) iii) Discuss the various evidences of organic evolution. (16mks)
a) i) - Gradual developmental change of species of organisms from simple forms of life into complex ones over a long period of time.
-Or Emerging of new forms of life from pre-existing ones gradually, over a long period of time.
ii) - Homologous structures – structures of common/similar embryonic origin but modified to perform different functions.
- Analogous structures- structures of different embryonic origin modified to perform similar functions.
b) Fossil/paleontological evidence
these are remains of organisms preserved in naturally occurring material like sedimentary rocks for many years.
They show morphological changes of organism over a long period of time egskull of man and leg of horse.
Comparative anatomy/taxonomy
Members of a given phylum/group show similarities
Such organisms have similar structures or organs performing the same functions eg digestive system, urinary system and nervous system.
Homologous structures have the same embryological origin but perform different functions eg the petadactyl limb.
Analogous structures have different embryological origin but perform same function eg wings of bird and those of insects.
Vestigial structures or organs which are greatly reduced and non-functional structures but have been well-developed and perform normal functions in the ancestors eg appendix and coccyx of man.
Comparative embryology
Vertebrates embryos in their early stages of development are morphologically similar suggesting that the vertebrates have a common ancestral origin.
Geographical distribution
Present continents are thought to have been one large land mass.
The continents slowly drifted apart over millions of years.
As a result of continental drift, isolation occurred bringing about different patterns of evolution, examples kangaroo and duck-billed platypus are only naturally found in Australia; jaguar and ilama found in South America resemble lions and camels found in Africa.
Comparative serology/physiology
Antigen-antibody reactions, Rhesus factor, blood groups and haemoglobin structure reveal some phylogenetic relationship among organisms suggesting common ancestry.
Comparative cell biology and biochemistry
Cells of most organisms contain common organelles, eg mitochondria and ribosomes as well as biological chemicals like ATP and DNA.
-Naming evidence;1mark;every statement ;1mark;total marks;18 but max;16
-Or Emerging of new forms of life from pre-existing ones gradually, over a long period of time.
ii) - Homologous structures – structures of common/similar embryonic origin but modified to perform different functions.
- Analogous structures- structures of different embryonic origin modified to perform similar functions.
b) Fossil/paleontological evidence
these are remains of organisms preserved in naturally occurring material like sedimentary rocks for many years.
They show morphological changes of organism over a long period of time egskull of man and leg of horse.
Comparative anatomy/taxonomy
Members of a given phylum/group show similarities
Such organisms have similar structures or organs performing the same functions eg digestive system, urinary system and nervous system.
Homologous structures have the same embryological origin but perform different functions eg the petadactyl limb.
Analogous structures have different embryological origin but perform same function eg wings of bird and those of insects.
Vestigial structures or organs which are greatly reduced and non-functional structures but have been well-developed and perform normal functions in the ancestors eg appendix and coccyx of man.
Comparative embryology
Vertebrates embryos in their early stages of development are morphologically similar suggesting that the vertebrates have a common ancestral origin.
Geographical distribution
Present continents are thought to have been one large land mass.
The continents slowly drifted apart over millions of years.
As a result of continental drift, isolation occurred bringing about different patterns of evolution, examples kangaroo and duck-billed platypus are only naturally found in Australia; jaguar and ilama found in South America resemble lions and camels found in Africa.
Comparative serology/physiology
Antigen-antibody reactions, Rhesus factor, blood groups and haemoglobin structure reveal some phylogenetic relationship among organisms suggesting common ancestry.
Comparative cell biology and biochemistry
Cells of most organisms contain common organelles, eg mitochondria and ribosomes as well as biological chemicals like ATP and DNA.
-Naming evidence;1mark;every statement ;1mark;total marks;18 but max;16
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