Evolution Flashcards
What is Evolution?
The process of biological change over time. It is based on the relationship between species and their environment.
What is the central idea of biological evolution?
All life on Earth share a common ancestor
What is decent with modification?
Evolution only occurs when there is a change in genetic material within a population over time.
What creates Long terms change in a species?
genetic inheritance
What are the 4 mechanisms of evolution?
Natural selection, Mutation, gene flow (migration), and Genetic Drift
What did Charles darwin realize?
He realized that all species evolved from common ancestors by means of natural selection
What is natural selection?
The way in which nature favors the reproductive success of some individuals in a population over others.
What are the 4 critical elements of natural selection?
Variation in traits, survival of the fittest, competition and adaptation
what does variation in traits mean?
Individual members of a species vary in physical characteristics. These physical variations can be passed on from generation to generation.
What does “Survival of the fittest” mean?
- the environment can’t support unlimited population growth
- not all individuals reproduce to their full potential
- you can use the survival of the fittest to refer to a situation in which only the strongest people or things continue to live or be successful, while the others die or fail.
What does competition mean?
- Members of all species compete with each other for limited resources
- Certain members are able to capture these resources better than others
What is adaptation?
Natural selection causes a population of organisms, and ultimately a species to become adapted to the environment
Each new generation includes more individuals that are better adapted to the environment
What are the Requirements of Natural Selection?
There must be an ability to survive and reproduce.
what is Genetic Variation?
Variation within a species is a result of the variety of combinations of alleles possessed by individuals
what are Mutations?
The source of all new alleles is mutation
Mutations are usually neutral or harmful
What is gene flow (migration)?
Changes in allele frequency between populations results in the loss or gain of alleles
Tends to reduce differences between populations therefore it is said to counteract natural selection
what is Genetic Drift?
When populations are small, chance can play a significant role in altering allele frequency
Can lead to fixation of alleles, which can increase the incidence of homozygous individuals which reduces genetic diversity
What are the 2 types of genetic drift?
Bottleneck effect and founder effect
what is the Bottleneck Effect?
When a severe event (flood, parasite, etc..) results in a drastic reduction in numbers, a population may experience a bottleneck effect
Only a very small sample of the alleles survive to establish a new population
Which alleles (individuals) survive is pure chance
What is the founder effect?
A small group from a large population leave and start a new population
The new population will have a different allele frequency then the original population
What are the 4 types of evidence for evolution?
Fossils, Dating, biogeography, structural form, and patterns in embryology
What are fossils?
Ancient remains, impressions, or traces of an organism preserved in rocks or other mineral deposits in Earth’s crust
How are fossils formed?
Formed when remains of an organism are gradually replaced with mineral deposits
Layers of silt or other debris accumulate and exert pressure on remains over time
What are the 2 dating methods?
Relative dating and absolute dating
What is relative dating?
sediments are deposited in layers over time
Deeper layers are older than those deposited on top
Does not determine the actual age of a fossil
what is absolute dating?
Determines actual age of a fossil
Methods include radiometric dating or counting tree rings
What is radiometric dating?
Scientists will measure the percentage of parent vs. daughter isotopes in a sample as the radioisotope decays
What is a fossil record?
Shows the history of life by showing the species that were alive in the past
Fossils found in young layers of rock, are more similar to today’s species than those in older deeper layers of rocks
Fossils appear in chronological order in rock layers
What are Transitional Fossils?
A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its descendant group
Shows characteristics common to two separate groups
What are vestigial structures?
structures that no longer serve the function in one species but serve function in another species that were evident in the organism’s ancestors
What Is Biogeography?
Study of past and present geographical distribution of organisms (used by Darwin and Wallace)
Species evolve in one location and then spread to other regions
Animals on islands resemble animals on nearby continents, suggesting that animals evolved from mainland animals
What are Patterns in Anatomy?
Homologous structure: structure with common evolutionary origin. The structures are similar in form but may serve different functions in modern species.
Analogous structure: structures that perform the same functions but evolve from different origins
What is Embryology?
Study of the pre-birth stages of an organism’s development, which can be used to determine evolutionary relationships
Similarities point to common ancestral origin
How does DNA play a role in proving evolution?
DNA from two organisms can be compared to determine how closely related they are
What are the 3 patterns of evolution?
Divergent evolution, Convergent evolution and coevolution
What is Divergent Evolution?
Two or more species diverge from a common ancestor
Species once similar to ancestor diverge and evolve independently and uniquely
what are the Results of Divergent Evolution?
Competition between species is minimized
New species diverge to fill specialized ecological niches
Given enough time, new species continue to evolve until most available resources are used
Leads to overall increase in biodiversity
Single species or group evolve to fill available ecological niches
What is Adaptive Radiation?
A form of Divergent Evolution
Definition: single species evolves into a number of distinct but closely related species
Each new species fills a different ecological niche
Occurs because a new variety of resources becomes available (not being used by other species)
What is Convergent Evolution?
When two different species evolve to occupy similar ecological niches
What is Coevolution?
One species evolves in response to the evolution of another species
“Evolutionary Arms Race”
One species evolves and gains advantage while other species evolves to keep up
What is speciation?
the evolutionary formation of a new species
what is Allopatric Speciation?
Speciation due to geographic isolation (physical barrier)
Unable to exchange genetic information
Over many generations, population will become less and less alike
What are the 2 types of speciation?
Allopatric
Sympatric
What is Sympatric Speciation?
Speciation as a result of populations splitting into separate gene pools
- Leads to reproductive isolation
Within the same geographic area
Rarer than allopatric speciation
Define Reproductive Isolating Mechanisms (RIMs)
Any behavioural, structural or biochemical trait that prevents individuals of different species from reproducing successfully together
What are the 2 types Reproductive Isolating Mechanisms (RIMs)?
Prezygotic mechanisms: RIMs that prevent interspecies mating and fertilization before the zygote can even form
Postzygotic mechanisms: RIMs that prevent maturation and reproduction in offspring from interspecies reproduction after the zygote forms
What are the types of Prezygotic Mechanisms?
Ecological isolation (physical), Temporal isolation(time, Behavioural isolation, Mechanical isolation, Gametic isolation
Ecological isolation (physical)
species occupy separate habitats or may live in the same habitat but do not encounter one another to reproduce
Temporal isolation(time)
reproductive cycles or mating occurs at different times
Behavioral isolation
species use different signals for attracting a mate (distinct mating rituals)
Mechanical isolation
structural differences in reproductive organs can prevent copulation
Gametic isolation
prevents fertilization at the molecular level by molecular markers
what are the 3 Postzygotic Mechanisms?
3 ways to prevent hybrids from reproducing:
Zygotic mortality: zygote or embryo fails to develop properly
Hybrid inviability: offspring experiences an early death
Hybrid infertility: offspring becomes strong and fit but is sterile
what is Mimicry?
In biology, it is resemblance of another organism in order to protect itself
It is a species “pretending” to be another species, so that predators will not try to hunt them
Organisms do not acquire these traits, but rather, are survivors after millions of years of natural selection in effect
