History of life I Flashcards
Natural selection is the result of these 3 principles
Darwin argues that natural selection is the result of these 3 principles
- Characteristic of organisms are inherited or passed from parent to offspring
- More offspring are produced than are able to survive
- Offspring characteristics varies, and those variations are inherited
Descent with modification
Gradual change in a species over time due to natural selection
Evolution
Natural selection is the driving force
- Only works if variation exists, variations come from genetic mutations.
- Diversity is further encouraged through sexual reproduction
Enviromental change leads to natural selection which leads to evolution
Divergent Evolution
When two species evolve in diverse directions from a common point
*flowering plants * ( same structure but looking very different.)
Convergent Evolution
Similar traits evolving in species that do not share a recent common ancestor.
Fossil shows a _________ of evolution
Progression
Physical Anatomy for evolution
Homologous structures
Similar structure but different functions
(Evolving from a common ancestor evolution)
Human arm, Whale flipper, & Bat wing
Vestigial structures
Body parts that lost their original functions due to evolution
Human appendix
Both structure provide support for the theory of evolution.
Embryologoy
Different species were once related
Mutations during embryo development can have big effects on an adult organism
Evidence for Evolution from biogeography
Locations of species helps us understand evolution
similar species are found on continents that were once connected
Molecular Biology: DNA as Proof
All living things have a DNA, proof they come from a common ancestor
Genetic code for making proteins is almost the same in all organisms
Sometimes, extra copies of genes appear, allowing one copy to mutate and evolve
Evolution is not a theory
Evolution is supported by tons of data, experiments, and observations over time.
Evolution Misconception’s
Individuals don’t evolve but populations do
mutations in DNA happen naturally
Evolution doesn’t explain the origin of the world but rather talks about how species change overtime
What are species?
Species is a group of organisms that can inbreed and have fertile offsprings
dogs, cats, humans
Speciation
- How new species form: happens when one species splits into two species over time
- Two groups must change incredibly to where mating can no longer happen
Two types of speciation
- Allopatric speciation (physical separation)
Group moves away (dispersal) or gets physically divided ( vicariance)
more distance creates more speciation
- Sympatric speciation (no physical separation)
New species evolves in the same area, caused by behavior changes or genetic differences
Adaptive Radiation
One Species, Many New Species
Original species evolve into multiple new species with different traits
Aneuploidy
- Sympatric speciation
-When an organism has an abnormal number of chromosomes
Auto polyploidy
- When plant’s cells fail to divide properly during mitosis, leading to extra sets of chromosomes
- When mitosis is not followed by cytokinesis
- Instead of 2n diploid chromosome these plants might have 4n (tetraploid) chromosomes
- Due to the mismatch the tetra plants cannot reproduce with the original diploid plants but can still reproduce with other.
Alloploidy
when two different species mate and produce hybrid offspring.
These hybrids can often have a combination of chromosomes from both species.
To produce offspring, these hybrids must go through a second mating event. Over time, these hybrids may become reproductively isolated
Polyploidy in Plants
Polyploidy (having multiple sets of chromosomes)
More than half plants species are related to ancestor that evolved through polyploidy
Mayjor evolutionary advantage help species form quickly & adapt to their environment
Reproductive isolation
- Prevents species from interbreeding two populations
-Prezygotic barriers:
Blocks reproduction from taking place, differing gametic & incompatible reproductive organs
- Post zygotic barriers happens after zygote formation
- Temporal Isolation: Species breed at different times.
- Habitat Isolation: Physical separation
- Behavioral Isolation: Mating rituals or behaviors prevent reproduction.
- Hybrid Zone: wo closely related species interact & reproduce creating hybrid’s
Rates of Speciation
Gradual Speciation: Species diverge at a slow pace, differing traits accumulating gradually
Punctuated Equilibrium: Species diverge quickly and then remain unchanged for long periods of time
Gene pool
Populations share a gene pool
Sum of all alleles in a population
larger gene pool = more genetic diversity
Allele frequency & Evolution
The percentage of a specific allele in a population
Evolution in genetics: Change in allele frequency over time
Population Genetics
Evolutionary forces (like natural selection and mutation) affect the genetic makeup of a population.
Alleles Frequency
Rate at which a specific allele appears within a population
Hardy Weinberg Principle of Equilibrium
- A population’s Allele & Genotype frequencies are stable unless evolutionary force acts
- It assumes conditions with no mutations, immigration, emigration or selective pressure for or against a genotype, infinite populations
Heritability
Fraction of phenotype variation that attributed to genetic differences or genetic variance
The more hereditability of a population’s phenotype variation, are more suspectable for evolutionary forces to act on heritable variation
Genetic Variation
Genetic Variation: The diversity of alleles and genotypes within a population
Inbreeding: leads to bringing together recessive mutations that could cause abnormalities’
Causes of change in genotype frequencies
Population’s allele and genotype frequencies can change because of:
*selection pressure, or driving selective force
*genetic drift or the effect of chance
Genetic drift
Genetic drift in a population can lead to the elimination of an allele from a population by chance
Bottleneck effect
Bottleneck effect: When a chance event or catastrophe reduce the genetic variability within a population
Small Populations are more susceptible to the forces of genetic drift
Founder effect
when the genetic structure changes to match that of the new population’s founding fathers and mothers.
Gene Flow
The flow of alleles in and out of a population due to the migration of individuals or gametes.
Nonrandom Mating
- Individuals not choosing mates randomly; lead to changes in a population’s genetic makeup.
- Causes of Nonrandom Mating:
Mate Choice (Assortative Mating) – Individuals prefer mates with similar physical
Physical Location – Individuals are more likely to mate with others nearby, which can limit genetic diversity.
Mutation
Changes to an organism’s DNA & an important driver of diversity in populations
Appearance of new mutations is the most common way to introduce novel genotypic and phenotypic variance.
