Evolution Flashcards
Evolution
Evolution is the slow process of a population changing over time
A population evolves and an individual mutates
Mutations can be harmful, helpful, or neutral
Mutations must be passed on for evolution.
Charles Darwin
Made the correct theory of evolution
Studied various animals
Came up with natural selection for finches.
Thought that they had one common ancestor
Ecological Niches
the way that a species acts and reacts in an environment.
Natural Selection
The environment will naturally reward the advantageous changes and eliminate the individuals with the unfavourable changes. Ex. Peppered Moth.
Artificial Selection
The process of humans selecting traits that we find desirable in species to change their population over time to fix our needs. Applies to both animals and plants.
Artificial Selection Steps
- Choose species to be bred in captivity
- Breed large number
- Choose trait
- Identify individuals who exhibit favoured traits
- Breed only them
- Repeat steps 4 and 5
Evidence of Evolution
To cause people to agree with natural selection, researchers were trying to show evidence.
They were looking for similar features which are called homologous features.
Homologous features
Structured in different species that resulted from a common ancestor.
These features do not have the same function
All mammals share similar bone organization in their arms
Analogous features
Features that serve similar functions but evolved from different sources
Features do not share common ancestors, showing that natural selection doesn’t favour one anatomy over the other if they accomplish the same task.
Embryonic development
Provides support for the theory of evolution.
In early stages, vertebrates look very similar.
Vestigial organs
Useless organs left behind.
If an organ doesn’t harm the individual, there is no selective pressure to remove the organ.
Three Types of Natural Selection
Directional Selection: when outlier trait is selected for→ pushes trait to the extreme. Ex. Long-necked giraffe.
Stabilizing Selection: occurs when the average range of traits is favourable. It reduces the number of extreme characteristics.
Disruptive Selection: selects against the average characteristics and favours both extremes.
Sexual Selection
Favouring any trait that specifically enhances the mating success of individuals.
Leads to males and females of species evolving appearances and behaviours different from each other.
Favours mating over any other trait.
Genetic Drift
Smaller population= traits can disappear by chance.
The population of 25 heterozygous individuals, they each have a 50% chance of having homozygous offspring.
If by chance, a majority of the population has homozygous dominant children, the homozygous recessive trait will decrease.
Genetic Bottlenecks
When a natural disaster occurs and a population is drastically reduced.
The smaller population could have a different gene distribution than starting population→ genetic drift.
Founder Effect
Small groups of individuals are separated from the rest of the population and they will evolve independently from the rest of the population.
If two populations get reunited, several generations later, they might not mate together anymore.
Hardy-Weinberg Principle
States if a population is large enough, and if there is no selective pressure, then allele frequencies will remain constant.
Assumptions of Hardy-Weinberg Equilibrium
- No selection
- No mutation
- No migration
- Large population
- Random mating
Speciation
When two populations of individuals are no longer able to reproduce to create successful offspring.
What are the two main types of speciation?
Prezygotic mechanisms: mechanisms that prevent species from having sex. This happens before fertilization.
Postzygotic mechanisms: prevent the fertilized egg from developing into a successful genetic individual.
Behavioural Isolation
When two populations attract mates in different ways → will not mate with another individual from another species.
Temporal Isolation
Mating species do not occupy the same environment → never meet to produce offspring.
Mechanical Isolation
The genitalia of the two species cannot mate properly for the exchange of genetic material.
Gametic Isolation
The sperm from one species does not recognize egg from another species.
Zygotic Mortality
The zygote is never able to properly form an embryo that will be able to survive the birthing process.
Hybrid Inviability
Hybrid forms but either dies before childbirth or never makes it to maturity.
Hybrid Infertility
Makes it to maturity but is infertile.
Allopatric Speciation
Occurs when a population is separated by geographic feature. Ex. Darwin’s finches.
Sympatric Speciation
Species evolve into separate species in the same area.
Results from a disruptive selection which selects extremes of a population.
Some of Darwin’s Finches started to eat large nuts and others ate small seeds which selected for both large and small beaks in the same population.
Main patterns of evolution
- Adaptive radiation
- Divergent evolution
- Convergent evolution
- Coevolution
- Gradualism
- Punctuated evolution
Adaptive Radiation
Occurs when a population rapidly evolves to fill multiple niches in the same area. Ex. Darwin’s Finches.
Results with several species sharing many characteristics because they are closely related.
Divergent Evolution
Happens over a long time span
Results in a population drastically changing traits to fill an ecological niche.
Ex. the taxon of rodents in Ontario.
Convergent Evolution
Two species evolve independently to fill the same ecological niche.
Usually occurs when an ecological niche is very large.
Many flowers evolve to fill different ecological niches.
Moths, birds, bees, bats, other insects ate nectar and evolved to create wings, but each wing evolved differently from the others.
Coevolution
When two separate species evolve to benefit from each other.
Moth and Madagascar flower
Gradualism
The theory that populations develop minor changes over a long period of time resulting in speciation.
Ex. by fossil records
Punctuated Evolution
Suggests that populations will not change for large stretches of time. The stretches will be punctuated by a rapid change in the population in a short time span, then the population will stabilize for a long time afterwards.
Punctuated Vs. Gradualism
Gradualism occurs in stable environments that remain relatively unchanged for long periods of time.
Less selective pressure to promote evolution.
Punctuated evolution occurs in environments that experience rapid changes. This caused populations to adapt quickly and drastically change the population very rapidly.
What are primates?
A group of mammals characterized by large brains relative to their size and flexible hands.
Ex. Humans
3 Groups of Primates
- Prosimian: group contains lemures and tarsiers
- Anthropoid: contains monkeys, apes and humans
- Humanoid: all of the species that are descendants of the common ancestor of chimpanzees and humans.
Australopithecus africanus
One of the most important ancestors.
First to walk on two legs
Since they could walk upright, they had an advantage.
Homo habilus
Mostly walks upright
Brain started to increase in size
Hands could carry things.
Homo erectus
First ancestor that was known to use fire to cook.
Started to develop hand axes out of stones.
Increase in brain size
Homo neanderthalenis
Lived alongside Homo sapiens for over 400,000 years.
Used tools and fire.
2 Theories for the extinction of Homo neanderthalenis
- Interbred with Homo sapiens and their traits were mostly lost over time.
- Homo sapiens killed them until they were extinct.
5 Major Mass Extinction Events
Ordovician Extinction Devonian Extinction Permian-Triassic Extinction Triassic-Jurassic Extinction Cretaceous-Paleogene Extinction
Current Mass Extinction
Holocene extinction has been caused by hunting, pollution and climate change.
