Evolution test Flashcards
Define evolution
Change in characteristics of a population that occurs over successive generations
Define adaptation
A structure,physiology (body mechanism or process) or behaviour that helps an organism survive better
Ex camouflage, walking stick behaviour
What is colour controlled by
A single heritable gene oh
Define natural selection
The process where the characteristics of a population change because individuals with certain heritable traits survive specific local conditions and pass on these heritable traits
What are the 3 conditions that need to be met for natural selection
Variation with the population
Differences in survival and reproduction (I.E Fitness) due to variation
Heritability of characteristics from parent to offspring
Explain why variation within the population must be met for natural selection
If we were all identical all of us would live and die the same way. Being different gives us each advantages and disadvantages in life. Chasing natural selection
Explain why differences in survival and reproductions due to variation must happen for natural selection
If all organisms were the same except one had a mutation, this mutation would increase chances of survival. BUT it is only an adaption if the mutation occurs in the offspring. Has to have an impact in the population over time. This ads will not fit into natural selection if it does not reproduce
Why does heritability of characteristics from parent to offspring have to happen for natural selection
If this mutation/fitness/special trait does not pass on the the offspring the mutation does not impact the population. Mutation must be inheritable
Define fitness
How well an organism “fits” into its current environment; greater the fitness the greater the chance of reproducing and Producing offspring who can survive to produce …”survival of the fittest”
What is selective pressure
Environment experts a selective pressure, thus selects for and against certain traits
Ex:the soot in Manchester
Or hunting or killing of individuals with a desirable trait (like elephant tusks example)
What are the four types of selection
Stabilizing
Disruptive
Directional
Sexual
What is stabilizing selection
Favours an intermediate phenotype (the physical representation of a genetic trait)
Reduces variation and improves the adaption of the population to aspects that remain constant
Bell chart
What is directional selection
When individuals at one end of the curve have higher fitness and are favoured more than individuals in the middle or at the other end
The result is a shift in the distribution curve in that direction
What is disruptive selection
When individuals at both of the extremes (upper and lower ends) of a trait are both more fit and are favoured over the average individuals in the population
What is sexual selection
When individuals of the same sex differ in their mating success and that differences is correlated to the presence of absence of a particular trait, that trait is said to be the result of sexual selection.
Traits that provide no benefit to survival that increase the likelihood of the male acquiring a mate are examples of sexual selection. The precedes of the trait may indicate genetic quality
What is female choice
Female has a greater cost to reproduction
Looking for good genes in the male to pass on to her offspring
What was George’s curviers theory for evolution
Discovered history of life was buried in layers in the rocks and that these layers tend to have unique groups of fossils and the deeper you go into the rock the more dissimilar life was from mordern life. saw that extinctions occurred and new species arrived. He proposed the theory of catastrophism.
Catastrophism: catastrophes destroyed species in an area and species that all ready existed repopulated area this no new species arose. They only move about
What was Jean Baptiste Lemarcks theory for evolution
Inheritance of acquired characteristics
Changes through use and disuse. Ex:giraffes neck, elephants trunk.
Also proposed that organisms were driven from simple to increasingly more complex forms. Life arises spontaneously in microscopic form and through the inheritance of acquired traits life became more complex until perfection is achieved
What was Charles Lyells theory for evolution
Uniformitarianism
Thought that the world changed at a uniform rate. In his mind the history of the world was vast without direction and that changes occurred at a uniform rate
(Without direction meaning not being guided by the supernatural)
Darwin applied these ideas into biological gradualism. Evolution occurred slowly and very gradually, and operate at a uniform rate
What was the 4 pieces of evidence Darwin had for uniformitarianism
1) life in temperate regions of South America were much more similar to life in South American tropics than life in European temperate regions
2) fossils found by Darwin looked very similar to living animals in the region
3) plants and animals living on the Galápagos Islands closely resembled life on the west coast of South America (nearest continental coast)
4) species of animals varied from island to island
Can evolution occur without genetic variation
No
Define biological species
Population that is reproductively compatible, producing fertile offspring
Define micro evolution
Changes in gene frequencies in a population; adaption within a species; accumulation of small changes may lead to new species
Define macro evolution
The evolution of a new species
What are the 5 conditions/events that can lead to microevolution
Mutation
Genetic drift
Gene flow
Non random mating
Natural selection (leads to adaption)
Why can mutations lead to microevolution
Random change in DNA may provide new trait variants which may provide the variation necessary for evolution to act upon.
Mutations must occur in gamete if it is to be passed on. If Mutation is a somatic cell (body cell) it cannot be passed on.
Mutation can be positive (selective advantage) or negative (harmful) or neutral
Why can genetic drift lead to microevolution
In a small population the frequency of genes (traits) can be changed drastically by chance alone. Survivors are not getter just lucky. Thus gene frequencies has changed in the next generation due to luck not adaption or selection pressure.
Ex: Singh’s blue eye club
Important effects on evolution:
Drift reduces genetic variation in populations, potentially reducing a populations ability to evolve in response to new selective pressures. Genetic drift acts faster and has more drastic results on smaller populations. Genetic drift is particularly important in rare or endangered species. Genetic drift can contribute to speciation. Ex: small population may diverge from large population through genetic drift
What is the bottle neck effect of genetic drift
Near extinction even drastically reduces population for at least one generation
Surviving population is not likely to represent the genetic variability of initial population. Genetic drift has a greater effect on a small population and genetic diversity is even further reduced
What is the founder effect of genetic drift
When a small number of organisms colonize a new area, it is likely that they do not represent the genetic variation of the parent population, thus genetic diversity is reduced and the small population is more prone to genetic drift
New environment means new selection pressures, and if this new environment is isolated and there is little influx of new genetic info the new selection pressures may cause speciation to occur
If a founder carried a genetic disorder the frequency of the genetic disorder being expressed will increase
Why can gene flow lead to microevolution
Gene flow is the movement of genes from one population to another. To avoid gene flow a population must be totally isolated.
Within a population: it can introduce or reintroduce genes to a population. Increasing the genetic variation of that population.
Across populations:
By moving genes around, it can make a distant populations genetically similar to one another, hence reducing the chance of speciation. The less gene flow between two populations, the more likely the two populations will evolve into two species
Why can non random mating lead to microevolution
Reduces genetic variation.
Individuals tend to mate with neighbour’s rather than members of a distant population
Inbreeding
Self fertilization(some plants)
Natural selection can’t work unless there is genetic variation within a population
Define assortative mating
When individuals pick partners who have similar phenotype to their own
Reduces genetic variation
Ex: artificial selection in dog breeding
Define speciation
The formation of a species
Requires populations to become genetically isolated- no gene flow
What are the two pathways for evolution
1) transformation (Anagenesis)- one species evolves into a new species, maintains biodiversity
2) divergence (cladogenesis)- when one or more species arise from a parent species that continues to exist, increases biodiversity
For a species to remain distinct what must remain
They must remain reproductively isolated. Species are generally separated by more than one barrier
What are the two Main types of barriers
Geographical barriers such as rivers or mountain ranges to keep populations separate
Biological barriers keep closely related species from interbreeding (presumptive and post zygotic barriers)
What is a prezygotic barrier and the 5 types
(Pre fertilization)
These barriers either impede mating between species or prevent fertilization of the egg If they do mate
The methods vary form sperm of a different species not being able to survive in the reproductive tact of the female to proteins on the surface of the cell membrane of the egg that will recognize sperm of the same species
Types: behavioural isolation, habitat isolation, temporal isolation, mechanical isolation, gametic isolation
What is behavioural isolation
Specific courtship rituals, Sony’s of birds, specific pheromones. These courtship rituals tend to be species specific and prevent interbreeding of closely related species
What is habitat isolation
Two species may live in the same region but occupy two different habitats and thus rarely meet
Ex: the northwest garter snaked like meadows while the common garter lives near water
What is temporal isolation
Species may occupy same habitat but mate or flower at different times of the year
What is mechanical isolation
Closely related species may be anatomically incompatible
Ex: genitalia of some insects act like lock and key, and different species genitalia will not fit
What is gametic isolation
Ensures that if gametes of a different species meet, that they will not fuse into a zygote
What is a post zygotic Barrier and the three types
If the sperm of a species fertilizes the egg of another specified, post zygotic barriers prevent hybrid zygotes form developing into fertile individuals
What is hybrid inviability
Genetic incompatibility may halt development or do the zygote (prevent mytosis)
What is hybrid sterility
Some species can produce an offspring who is sterile ( ex horse and donkey produce a mule) because meiosis fails due to genetic incompatiblity (differences in chromosome number and or structure)
What is hybrid breakdown
First generation hybrids are sometimes fertile but when hybrids mate with other hybrids or member of parent species, the offspring are sterile or weak
What is sympatric speciation
When populations become reproductively isolated without geographic isolation. Animals may become reproductively isolated within a population as they begin to use resources not used by the parents population. This will lead to non random mating and then speciation
Ex: lake Victoria has 500 species of cichlid fish all derived from one common ancestor. Each species evolved as individuals began to exploit and adapt to different habitats/conditions within the lake
5 ways allopathic speciation/ geographic speciation occurs
All ways may work individually but usually together to allow speciation to occur over time
1) small populations that become isolated from parent populations are likely to go through speciation
2) isolated populations tend to exist on the edge of the parent population range, being on the edge they may have slightly different gene pool than minority of population due to gene flow at the edge
3) if a periphery group is isolated that is already genetically different than parent population, they are subject to founder effect
4) since the isolated group is a small population it is now affected by genetic drift, where new mutations or new gene frequencies may be more prevalent simply by chance
5) or the isolated population is living in a habitat with different selection pressures Thant the parent population, natural selection may change population
What is adaptive radiation
A surge of evolution from an original ancestral form as new forms “fan out “ ; adapting over time to new niches. Ex: the Galapagos finches examined by Darwin, all presumably descended from a common ancestral species, but each of which had a different mode of life
Major occurrences of adaptive radiation occur when
After the evolution of a novel trait
Ex the evolution of wings on an insect allowed the exploitation of thousands of new habitats /niches
After mass extinction events there tend to be what
Periods of rapid adaptive radiation
Ex: the extinction event that killed the dinosaurs and cooled the earths climate allowed for the adaptive radiation of mammals which were Rodent size during the time of the dinosaurs
What is divergent evolution
Pattern where species that were once similar to ancestor diverge and become dissimilar
What is convergent evolution
Similar traits arise in completely separate species as each has independently adapted to similar environmental conditions
Ex: bats and birds both have wings and fly
What is co evolution
When two species who are tightly associated with each other (predator and prey) evolve together, responding to changes in the other population
Ex: as cheetahs evolved to be faster to catch prey the Thompson’s gazelle has evolved incredible speed as well, as an adaption to the selection pressures placed upon them by the cheetah
Ex: rough skinned newt has evolved incredibly toxic Venom secreted from skin in response to genetic variants of garter snake who have evolved resistances to newt toxin. ARMS RACE
What are the two hypotheses for the pace of evolution and explain
1) gradualism- slow, gradual change over time
2) punctuated equilibrium- long periods of no change as environment is stable, then a period of rapid change followed by long periods of no change as environment is stable again
What are the three types of adaptive radiation
Divergent evolution
Convergent evolution
Co evolution
