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How Do We Know Organisms Evolve? - Coggle Diagram
How Do We Know Organisms Evolve?
4 Main Ideas About Evolution
Variation
Individuals in a population or group differ in some trait on interest
Inheritance
The variation in the trait of interest is at least partially inherited
Differential survival & reproduction
More offspring are born than can survive
Adaptation
The frequency of the trait that helps individuals survive and leave more offspring will increase in a population over time, as will the alleles of that trait
Evidence of Evolution
Anatomy
Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
Molecular biology
DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
Biogeography
The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Fossils
Fossils document the existence of now-extinct past species that are related to present-day species.
Direct observation
We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects; superbugs)
Superbugs & anti-biotic resistance
5 Fingers of Evolution
Small population size (pinky finger)- a population can shrink or a small population in general can have a smaller gene pool. This is known as the founder effect or a genetic bottleneck.
Nonrandom mating (ring finger)- choosing a mate based on a particular trait can change the gene frequency in a population. This can cause one phenotype to be preferred over another, can cause one phenotype to become prevalent, while another one dies out.
Mutations (middle finger)- changes in genetic code can cause a change in a gene, and this in turn can cause a change in how a protein functions. The change in protein function can affect the survival of the individual, which can change the frequency of the gene in the gene pool.
Gene flow from emigration/immigration ( pointer finger)- when there is significant flow of new arrivals or a great number of departures from a population, the gene frequency in the gene pool is affected.
Adaptations- advantageous traits that allow an organism to live, while organisms with disadvantageous traits will die out.
Micro Evolution
Mutation
Natural Selection
Gene Flow
Genetic Drift
Macro Evolution
Geographical Isolation
Becoming physically separated from the rest of the species.
Temporal Isolation
Rare interbreeding because of different timings
Behavioral Isolation
Behavior needed for mating is not present
Biology of Skin Colors
Cells of individuals near the equator - with high pigmentation
High UV
Normal folate
Normal vitamin D
More melanin
Cells of individuals near the equator - with low pigmentation
High UV
Low folate
Normal vitamin D
Less melanin
Cells of individuals in the northern hemisphere - with high pigmentation
Low UV
Normal folate
Low vitamin D
More melanin
Cells of individuals in the northern hemisphere - with low pigmentation
Low UV
Normal folate
Normal vitamin D
Less melanin
Selection
Types
Directional - a change in the environment shifts the spectrum of observed phenotypes
Diversifying/ Disruptive - two or more extreme phenotypes are selected for, while the average phenotype is selected against
Stabilizing - an average phenotype is favored
Pressure
Resource availability
Presence of sufficient food, habitat (shelter / territory) and mates
Environmental conditions
Temperature, weather conditions or geographical access
Biological factors
Predators and pathogens (diseases)
Cladograms & Phylogenetics
Show relationship between species and ancestors
Key Terms
Homologous Structures
refer to species from a common ancestral origin evolve similar anatomical parts but with dissimilar functions.
Analogous Structures
biological structures with comparable functions and yet they differ in regard to the developmental origin and anatomical features
These are a result of convergent evolution
Vestigial Structures - organ is one that an organism has, but doesn’t use or is not needed
Relative Dating - actual age of fossil is unknown
Divergent - The type of evolution where species gradually become increasingly different from their ancestors.
Convergent evolution occurs when species evolve analogous structures in spite of their evolutionary ancestors being very distant or unrelated.