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.
What is allele frequency?
Allele frequency is the number of organisms carrying a particular allele.
Define Genotype frequencies
Genotype frequencies refer to the number of individuals carrying a particular genotype.
What does the Hardy-Weinberg equilibrium principle state?
The Hardy-Weinberg principle states that allele frequencies remain constant if certain conditions exist.
When does the Hardy Weinberg principle hold?
The principle holds if there is no genetic drift, mutation, or gene flow.
What are the factors that produce changes in population?
Factors producing changes in population include crossing-over, independent segregation, random fertilization, mutation, natural selection, non-random breeding, genetic drift, genetic load, and gene flow.
Describe Non-random mating
Non-random mating occurs due to structural and behavioral mechanisms.
What is Genetic drift
Genetic drift is the change in gene frequencies by chance.
What is the Founder principle?
The Founder principle is when a small population becomes split off from the parent population.
Define Genetic load
Genetic load is the existence of disadvantageous alleles.
Define Gene flow
Gene flow is the interchange of alleles between populations.
Define natural selection
Natural selection is the process where better-adapted organisms survive and reproduce.
How does natural selection occur?
Natural selection occurs through competition for resources and selective pressure.
How does natural selection cause an evolutionary change?
Natural selection causes evolutionary change by changing allele frequencies.
What are the three types of natural selection?
The three types of natural selection are stabilizing, directional, and disruptive selection.
What is Stabilizing selection?
Stabilizing selection favors phenotypic features near the mean.
What is Directional selection?
Directional selection operates in response to gradual changes in environmental conditions.
What is Disruptive selection?
Disruptive selection favors the presence of more than one phenotype.
Describe how drug and pesticide resistance occurs
Drug and pesticide resistance occurs through random mutations and selection pressure.
Describe how Heavy metal tolerance in grass and other plants came to be
Heavy metal tolerance in plants occurs through mutations that trap or excrete heavy metals.
What is Industrial melanism?
Industrial melanism is the increase in frequency of melanic forms of peppered moths due to air pollution.
What is Polymorphism?
Polymorphism is the existence of two or more forms of the same species.
What are the two forms of polymorphism?
The two forms of polymorphism are transient and balanced.
What is Balanced polymorphism?
Balanced polymorphism occurs when different forms co-exist in a stable environment.
What is Transient polymorphism?
Transient polymorphism arises when morphs undergo strong selection pressure.
What is Outbreeding?
Outbreeding involves crossing individuals from genetically distinct populations.
What is hybrid vigor?
Hybrid vigor is the superior phenotypic characteristics of hybrids.
What is the disadvantage with outbreeding?
The disadvantage of outbreeding is that it makes consistent qualities harder to achieve.
What is the advantage of outbreeding?
The advantage of outbreeding is that it results in healthier and stronger hybrids.
What is Inbreeding?
Inbreeding involves selective reproduction between closely related organisms.
What is the disadvantage of inbreeding?
The disadvantage of inbreeding is that it reduces fertility and viability.
Define speciation
Speciation is the process by which one or more species arise from previously existing species.
What are the types of speciation?
The types of speciation are allopatric and sympatric.
Define Allopatric speciation
Allopatric speciation occurs due to spatial separation of a population.
Define Sympatric speciation
Sympatric speciation occurs when organisms inhabiting the same area become reproductively isolated.
Define isolating mechanisms
Isolating mechanisms produce and maintain reproductive isolation.
Define Reproductive isolation
Reproductive isolation refers to the existence of biological factors that impede interbreeding.
What are pre-zygotic mechanisms if reproductive isolation?
Pre-zygotic mechanisms include seasonal, ecological, behavioral, physiological, and mechanical isolation.
What are Post zygotic mechanisms of reproductive isolation?
Post-zygotic mechanisms include hybrid inviability, hybrid sterility, and
How does inbreeding affect a natural population?
- Reduces variation in the population
- Reduces vigor
- Decreased resistance to disease
- Less adapted to environmental change
- Easily become extinct
- Reduces potential for evolutionary change
However:
- Maintenance of desirable characteristics
