Evolution Flashcards
What is evolution?
Evolution is the gradual process which takes place over a long period of time in which more complex organisms develop from pre-existing simpler organisms
What are the theories of the origin of life?
- Special creation theory
- Steady state theory
- Spontaneous generation theory
- Cosmozoan theory/ the pans Permian theory
- Biochemical evolution/ biogenesis
Describe Lamarckian theory of evolution
The theory was based on two conditions that is “the use and disuse of structures and the inheritance of acquired characteristics”.
He explained that in the life of an organism, a change in environment may lead to changed patterns of behavior which can necessitate new or, increased use (or disuse) of certain organs or structures.
Extensive use would lead to increased size and or efficiency while traits acquired during the lifetime of the individual were believed to be heritable and thus transmitted to offspring.
What is an example according to the Lamarckian theory of evolution?
According to Lamarck, present day long-necked giraffes obtained their long necks from their short-necked ancestors through the same process.
As the short-necked giraffes stretched to reach leaves on tall trees, it created a small elongation of the neck and that was passed onto the next generation and further stretching of the neck, to feed in tall trees, the neck became longer in the proceeding generations.
What are the criticisms of Lamarckism?
Acquired traits, though affecting the phenotype, are non-genetic and having no influence on the genotype cannot be inherited.
What are the essential features of Darwin’s theory?
- Over production of off springs; He believed that all organisms produced a large number of off springs which would lead to an increased size of the population.
- Constancy of numbers, despite the tendency of organisms to increase in number due to over production of species, most population maintained relatively constant numbers. The majority of off springs die before they are able to reproduce.
- Struggle for existence; He concluded on the basis of the above two that members of the species were constantly competing with each other with effort to survive. In this struggle for existence, only few would live for long enough to breed.
- Variation among off springs; they sexually produced off springs of any species to show individual- variation that no two off springs are identical.
- Survival for the fittest by natural selection; among the variety of off springs, some are better adapted to withstand the prevailing conditions than others. I.e. some will be able to survive in the struggle for existence; such types are more likely to survive long enough to breed.
- Like produce like; those survived to breed are likely to produce off springs similar to themselves. The advantageous characteristics which gave them a win in the struggle for existence are likely to be passed on in the next generation.
- Formation of new species; Individuals lacking favorable characteristics are less likely to survive long enough to breed and over many generations; their numbers decline. The individuals with favorable characteristics breed with consequent increase in their number. The inheritance of one small variation may not be itself producing new species. However, the development of a number of variations in a particular direction over many generations gradually leads to variation of a new species.
What does Darwin’s law of natural selection state?
Darwin’s law states that favored characters are selected for, while unfavored ones are selected against.
How did Darwin explain the development of the long-necked giraffes?
Darwin explained long-necked giraffes through natural selection, where short-necked giraffes died off, and long-necked ones survived and reproduced.
What are the limitations of Darwin’s theory?
Limitations: Darwin’s theory doesn’t explain life’s origin, and has been misinterpreted as “survival of the fittest” and contradicts religious beliefs.
Define Paleontology
Paleontology is the study of fossils.
What is the weakness of paleontology?
Weakness: Fossil records are incomplete, with missing links.
What are the explanations for the gaps or incompetence of fossil record?
Gaps in fossil records are due to decomposition, scavenging, soft-bodied organisms, and limited discovery.
How can the discontinuous distribution of species can be explained?
Discontinuous distribution is explained by adaptive radiation, genetic isolation, and continental drift.
What are homologous organisms?
Homologous organisms have similar basic forms, microscopic structures, and embryonic development.
What are examples of homology?
Examples: Flower structures, pentadactyl limbs, and brachial arches.
What does the existence of homologies within a group of organisms suggest?
Homologies suggest descent from a common ancestor and close phylogenetic relationships.
What is adaptive radiation?
Adaptive radiation is the modification of homologous structures for different environments and modes of life.
When is the significance of adaptive radiation?
Significance: Suggests divergent evolution based on modification of homologous structures.
What are vestigial organs?
Vestigial organs are homologous structures with no apparent function, such as the human appendix.
What are analogous structures?
Analogous structures are similar structures in different organisms that perform the same function.
What does the existence of analogous structures suggest?
The existence of analogous structures suggests convergent evolution.
What features are possessed by embryos of vertebrates at comparable stages?
Embryos of vertebrates have external branchial grooves, segmental myotomes, and a single circulation.
Give examples of biochemical homology
Examples of biochemical homology include proteins like cytochromes and hormones like prolactin.
What is a Gene pool?
A Gene pool is the total variety of genes and alleles in a population.
What does a population whose gene pool shows consistent change from generation to generation suggest?
A changing gene pool suggests evolutionary change.
Explain what a static gene pool is
A static gene pool has inadequate genetic variation for evolutionary change.
