Evolution (General) - Unit 3 Flashcards
Give an overview of what evolution is.
- The changes in the heritable characteristics of living organisms over time
- The theory that all species on earth are descendants of a common ancestor
- Evolution is both a fact and theory
> fact: observation that has been repeatedly confirmed
> theory: a well supported explanation that incorporates facts, laws, inferences and tested hypotheses - Survival of the fittest
- Biological fitness: ability to survive and reproduce
> Organism with ‘fitter’ alleles survive and pass them on - Varying interactions between species and the environmental changes causes some species to go extinct while others thrive
Give an overview of what adaptation is.
- Physical, structural or behaviour of an individual that helps it survive for generations
- Enables organisms to survive and escape predators
- Occurs as a result of environmental limits or changes
- Provide a biological advantage that improves chance of survival
Types of adaptation
- Structural adaptations: physical features of an organism
> Camouflage = a defense mechanism or tactic organisms used to disguise and blend in with surroundings to escape predators, helps avoid predation
> Mimicry = disguise as a harmful species to avoid predation, imitating inedible species as a protection mechanism
- Behavioural adaptations: Things/actions organisms do to survive
> ex. possums play dead, rabbits freeze
- Physiological adaptation: changes or chemical reactions within an organism
> Hibernation = allows survival of harsh conditions by preserving energy
- Adaptations are a result of gradual, accumulative changes that help an organism survive and reproduce
- Adaptations are a result of genetic mutations in an organism’s DNA
- These mutations must be heritable in order for the adaptation to persist
- Due to mutations, there are many variations that appear in the population
Give an overview of what variation is.
- Differences between individuals which may be structural, functional, or behavioural
- Not all variations become adaptations
- Environmental conditions determine whether the variation is beneficial or not
- Environmental conditions change
- Eventually variation may become more frequent in the population and become a trait
- A characteristic may not be beneficial now but environmental conditions could change that
- Genetic variation: in a population is due to the variety of genes within each individual
Give an overview of what mutation is.
- Permanent change in the genetic material of an organism; provide new alleles, random and spontaneous
- Occurs when DNA is copied before division (synthesis)
- Caused by UV radiation, chemicals, alcohol, drugs
- When there is a mutation in DNA
- Cells could die
- Cells could malfunction
- Reproduce too rapidly (cancers)
- These mutations in the nucleotide sequence create new versions of alleles
- Source of all genetic variation is mutation
- Not all mutations are heritable
> ex. mutations in somatic cells - Beneficial mutations provide selective advantage depending on the environment
> this selective advantage can become more prevalent in the population
> affects the ability of the population to survive
What is a selective pressure? What are the three types of selective pressures? Name and explain.
Selective pressure: some sort of factor that presents a challenge to the population
- Only individuals with adaptations or specific traits can survive long enough to reproduce and overcome the challenge
- Individuals w/o adaption will likely die before mating
Natural selection: process that determines which characteristics will be inherited in a population over time
- Result of biotic and abiotic factors
> Biotic includes predators, competition for resources, parasites
> Abiotic includes: weather, urban vs rural, pesticides, antibiotics
- Natural selection is never intentional, can not anticipate environmental change
Artificial selection: selective pressure exerted by humans on populations in order to modify desirable traits
- Biotechnology: use of tech and organisms to produce useful products
- Artificial selection done on crops
> To increase nutritional value
> Increase production at harvest
> To be drought-resistant or pest resistant
- Consequences
> Severe side effects (ex. dogs)
> Monoculture = planting of the same type of species (genetically identical), reduces genetic diversity and wipes out all crops at once
> Gene banks- seeds of plants are preserved for genetic combos to be available to farmers, genes are collected–
Sexual selection: natural selection for mating based on competition between males
- Sexual dimorphism: sexes of same species exhibit different morphological characteristics especially males having traits that attract females
- Increases allele frequency of popular mating males and decreases others
- Most traits which natural selection acts on are polygenic
Natural selection can be further divided. What are the three modes of natural selection? (Hint: think of a graph we’ve been given)
- Stabilizing selection: favouring of intermediate phenotypes and acts against extreme variants
> ex. grey fur is favored over white or black - Directional selection: one extreme phenotype is favoured over the other, the curve is towards preferred extreme
> ex. larger beaks are favoured over smaller and medium - Disruptive selection: extreme phenotypes are preferred over intermediate phenotypes, may result in the elimination of the intermediate
> ex. black and white fur is preferred over gray fur
What is microevolution?
Changes in allele frequency over time.
What are the five mechanisms of evolution?
Mutation: random spontaneous changes in DNA sequence of chromosomal mutations
> ex. two green frogs produce a brown frog, or antibiotic resistance
Non-random mating
- Preferred phenotype: sexual selection, decreased genetic diversity
> ex. peacocks
- Inbreeding: closely related individuals breed together, can cause deformities
> ex. dog breeds
Gene flow: flow of alleles in and out of a population due to migration, increases genetic diversity by introducing new alleles or changing distribution of existing alleles
> ex. grey wolves travel long to find breeding partners like white wolves
Genetic drift: change in allele frequencies due to chance in breeding population, decreases genetic diversity, affects smaller populations more than large
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Bottleneck effect: rapid loss of alleles due to large decrease in population due to hunting, severe weather, disease, etc.
- Causes limited diversity and different population
> ex. survivors on pingelap island
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Founders effect: rapid loss of alleles when individuals start a new isolated population away from the original
- Limited diversity
> ex. Amish people
What does speciation require?
- Initial isolating barrier (factors prevent gene flow)
- Some kind of divergence (mutation, natural selection, genetic drift)
- Reproductive isolating barriers: when two populations become so different out of divergence, reproduction becomes difficult
What is macroevolution?
Large scale changes in organisms.
What are the two forms of speciation?
Allopatric speciation
- Evolution of a population due to geographic isolation
- Geographic reproductive barriers
- Species become so distinct they can not breed once brought back together
> Isolated species become extinct or the population evolves into different species
Sympatric speciation
- Occurs when population in the same geographic location diverge due to non-random mating or chromosomal changes
- Species that occupy the same place at the same time begin to diverge, due to genetic differences
- Eventually these genetic differences would prevent mating with each other
- Speciation in which populations with the same geographic area diverge and become reproductively isolated
Compare prezygotic and postzygotic isolation.
Prezygotic (prevents fertilization or mating)
- Difference in timing of reproductive cycle
- Difference in courtship behavior and chemical signals
> pheromones
> different songs
- Difference in habitats
- Difference in reproductive organs (lock and key)
- Mechanical isolation: right hand vs. left hand
- Gametic isolation: difference in molecular markers
> ex. red and purple sea urchins, two closely related species are incompatible, will not fuse
Post-zygotic (sperm and egg produce hybrid zygote)
- Can prevent development into viable fertile individuals
- Hybrid inviability/zygotic mortality: unlikely to survive long/fertilization takes place but zygote does not survive or does not survive long after birth
- Hybrid sterility (infertile): offspring becomes sterile
- Hybrid breakdown: 1st gen is viable fertile, 2nd gen is weak or sterile (deterioration in viability and fertility)
What are the pathways of evolution?
Divergent evolution
- Species with similar ancestors diverge or become increasingly different due to differences in selective pressures
- Forelimbs in mammals are similar in structure but differ in function due to diff. Selective pressures (homologous structures)
- Adaptive radiation: several different species form from a common ancestor due to a variety of selective pressures in isolated geographical areas
Convergent evolution
- Evolution in which analogous (similar) traits arise independently in different species due to the same selective pressure
> ex. marsupial and mammals
Co-evolution
- Influence of closely associated species on each other in their evolution
- Evolutionary pathways become linked in which one species evolves on a response to the evolution of another species
> ex. fig plants depend on wasps for pollination
What are the three rates of evolution (speciation)?
Gradualism
- Gradual, slow changes where each species is similar to original species
- Transitional forms present
Punctuated equilibrium
- Quick bursts of rapid evolution followed by long periods of low evolution
- Due to mutation or major changes in environment
Combination of both
- Belief that both types of evolution may occur
Give evidence for evolution. DO NOT EXPLAIN!
- Fossil records
- Biogeography
- Anatomy
- DNA
- Embryology
