Evolution Flashcards
Evolution
The process of change overtime, specifically, a change in the frequency of a gene or allele in population overtime
Natural Selection
Organisms that are best adapted to an environment to survive and reproduce more than others
What are the 4 steps of Darwin’s Natural Selection?
- Overpopulation
- Variation
- Competition
- Selection
Darwins Natural Selection: Overpopulation
each species produces more offspring than can survive
Darwins Natural Selection: Variation
Each individual has a unique combination of inherited traits
Adaptation
An inherited trait that increases an organism’s chances of survival
Why is variation important?
- environmental changes
- the more variation within a species, the more likelihood to survive
Darwins Natural Selection: Competition
Individuals compete for limited resources
- food
- water
- space
- mates
When does natural selection occur?
Competition - “survival of the fittest”
Fitness in Natural Selection
the ability to survive and reproduce
True or False: all individuals survive to adulthood
False
Darwins Natural Selection: Selection
The individuals with the best traits/adaptations will survive and have the opportunity to pass on it’s traits to offspring
True or False: Natural selection acts on the phenotype not the genotype?
True
What is descent with modification?
each living species had descended, with changes, from other species over time
What is Common Descent?
all living organisms are related to one another
Types of Evidence of Evolution?
- Fossil Records
- Transitional Fossils
- Archaeopteryx
- Homologous body structures
- Analogous structures
- vestigial Organs
- Embryology
- Biochemical Evidence
Fossil Records
a record of the history of life on earth
Transitional Fossils
Fossils or organisms that show the intermediate states between an ancestral form and that of it’s descendants are referred to as transitional forms
Archaeopteryx
missing link between reptiles and birds
Homologous Body Structures
similar anatomy in different types of animals because of an common ancestor
Analogous Structures
Similar features of different animals that have evolved due to convergent evolution.
When two different species live in similar environments, they often evolve similar
Do Analogous Structures share a common ancestor?
no
Vestigial Organs
“leftover” traces of evolution that serve no purpose
Embryology
embryos of all vertebrates are very similar early on
Biochemical evidence
DNA with more similar sequences suggest species are more closely related
Gene pool
the variety of genes that can be selected from an environments population
Speciation
the formation of a new species
Microevolution
Evolutionary change within a species or small group of organisms, especially over a short period of time
Macroevolution
Major changes among species occurring over a long period of time
Pressures
drive change in a certain direction
Recipe of Evolution
Variation→Pressure→Selection→Time
Types of Pressures
- Natural Selective Pressures
- Artificial Selective Pressures
Natural Selective Pressures
created by natural forces that exist in nature
Examples of Natural Selective Pressures
- Resource Availability
- Environmental Conditions
- biological Factors
Resource Availability
presence of sufficient food, habitat (Shelter/territory) and mates
Environmental Conditions
Tempture, weather conditions or geographic access
Biological Factors
predators and pathogens
Artificial Selective Pressures
created international or unintentionally by humans
Example of Artificial Selective Pressures
- International Artificial Selection
- Unintentional Artificial Selection
International Artificial Selection
A pressure that has been created on a population with an international effect
Unintentional Artificial Selection
a pressure that has been created based on human action that has an unintentional effect on population
Types of Selection
- Directional
- Stabilizing
- Disruptive selection
Directional Selection
Shifts the range of variation in traits in one direction
Stabilizing Selection
Favors intermediate forms of a trait
Disruptive Selection
Favors forms of a trait at the extremes of a range of variation
Sexual Selection
natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. (matting)
Species
A species is defined as organisms that can reproduce and produce viable offspring, meaning their offspring are also able to reproduce
How does Speciation occur?
New species arise when populations are isolated in some way, different mutations occur and build in the two different groups
Reproductive Isolation leads to…
speciation
Patterns of evolution
- Divergent
- Convergent
- Parallel
Divergent Evolution
Occurs when one species becomes two entirely isolated subpopulations and finally two new species
what does Divergent Evolution lead to?
Homologous Structures
Convergent Evolution
Occurs when two different species that are NOT closely related independently evolve similar traits as a result of having to adapt to similar enviroments
What does Convergent Evolution lead to?
Analogus Structures
Parallel Evolution
occurs when independent species acquire similar characteristics while evolving together at the same time in the same ecospace.
Isolation Events (that lead to speciation)
- Geographic Isolation
- Behavioral Isolation
- Temporal Isolation
Geographic Isolation
a physical barrier that separates two groups of a population, such as a river, mountain range or ocean
Behavioral Isolation
two populations are capable of breeding but are isolated by difference in courtship rituals or other types of behavior associated with mating.
Temporal Isolation
Species become isolated by reproducing at different times
