Unit 7 - Natural Selection Flashcards
Adaptation
inherited characteristics that increase chances of survival and reproduction
Darwin’s Argument
- variations exists in populations that is an inherited trait
- more individuals are born than can survive
- individuals with traits better suited for to their environment will survive and reproduce
- unequal ability of organisms to survive leads to higher frequency of better traits/ high value traits
Fitness
measure of survival and reproduction
High fitness
traits will allow to produce + survive (ex. Speed in a predator )
What happens if the environment changes?
natural selection
Natural Selection
nature selects survivors so organisms that are better suited for the environment survive and reproduce
Natural Selection Results from
- predators, lack of food, temp, pollution
- gradual changes accumulate and less favorable ones will diminish
The peppered moth
in 1850’s in England, trees near factores were covered in soot which led to an increase in dark phenotype and decrease in peppered phenotype
Can an organism just adapt by mutating?
No
Can an individual choose to change its phenotype to suit its environment?
no
does the environment cause a mutation to occur?
no it’s not the environment, it’s the DNA sequence that causes a mutation to occur.
what happens if a population lacks genetic variation and the environment changes?
the population can possibly go extinct
what happens if a mutation arises in an offspring that results in an adaptation that increases the chance of surviving and reproducing?
phenotype will increase in future populations
stabalizing selection in a graph
selection towards the middle
directional selection in a graph
This occurs when one extreme of a trait is favored over the other. Over time, the population shifts in one direction
Diversifying selection/ disruptive in a graph
This occurs when both extremes of a trait are favored over the average. This can lead to a split in the population, where two different types may emerge.
Convergent Evolution
species that have similar traits but do not share a common ancestor (environmental pressures) ex. shark and dolphin
Ecological Niche
organisms role in its environment (ex. bees pollinate flowers, when organisms eat and mate)
Divergent vs. Convergent
convergent: similarities due to enviormental pressures
divergent: similarities due to a common ancestor
Divergent Evolution
similarites due to a common ancestor
What are the mechanisms through which populations can evolve?
Natural Selection
Sexual Selection
Mutations
Genetic Drift
Bottleneck Effect
Founder Effect
Gene Flow
What does it mean to evolve?
changes in allele frequency in ppopulatiosn overtime
Interdependent Sexual Selection
Females select mates based on certain desirable traits
Intradependent Sexual Selection
Males compete among themselves for access to mates
what does interdependent and intradependent both lead to?
sexual dimorphism
Sexual Dimorphism
the physical differences between males and females of the same species beyond just reproductive organs
Mutations
Random changes in DNA that create new genetic variations
- ultimate source of variety
- ex. multi colored bugs
Genetic Drift
A random change in allele frequencies due to chance, especially in small populations. It’s not based on natural selection. ( population size is limited )
Natural Selection
The process where organisms with traits that help them survive and reproduce pass on their genes, while those with less favorable traits die off.
Sexual Selection
A form of natural selection where traits that increase reproductive success (even if they don’t help survival) become more common.
Bottleneck Effect
A drastic reduction in population size due to an event (like a disaster), which reduces genetic diversity
how do you get new variations?
mutations
Founder Effect
When a small group of individuals starts a new population, leading to reduced genetic variation and possible unique traits.
Gene Flow (Migration)
new indiviuals move into an area; migration into a population + adding to existing population
what are the adaptive mechanisms of evolution?
natural and sexual selection
what are the random mechanisms of evolution?
mutations, genetic drift, gene flow, bottle neck effect, founder effect
How can we measure if a population is evolving?
hardy weinberg
if a population is in hardy weinberg that means?
non of the 5 mechanisms are happening anf they are not evolving from one generation to the next
Evolution is supported by scientfic evidence from many disciplines. They are..
- geographical
- physical
- geological
- mathematical
- biochemical
Geographical Evidence
shows the distribution of organisms on the planet where similar organisms were found in completely different places
Geological Evidence
Fossil evidence
Physical Evidence
- homologous structures
- analogous structures
Homologous Structures
divergent evolution
- similar structure, different function
Analogous Structures
convergent evolution
- similar structure, same function (ex. bird wings, fly wings)
Biochemical
comparing DNA, proteins, amino acids, RNA
- more similarites the closer the relation
Mathematical
Hardy Weingberg to determine the frequency of changes in alleles in populations
Fossil Record
- oldest fossils are deep down
- youngest are going to be closer to the surface
- vestigal structures
Morphological Homologies
structural similarities between different species that indicate a common ancestor.
- embryology: similar features during development
What processes are conserved across organisms?
- glycolysis
- DNA replication
- protein syntheis
What structural and functional evidence show relations?
- DNA
- cell membrane
- proton gradient to make ATP
Describe the process of antibiotic resistance in bacteria.
Bacteria evolve quickly due to rapid reproduction. When exposed to antibiotics, most die, but some with random mutations may survive and reproduce, passing on resistance genes. Over time, this can lead to entire populations becoming resistant, reducing the effectiveness of antibiotics.
Pesticide Resistance
Evolution in Insects; insects evolve resistance when exposed to pesticides.
Cladograms
used to show the evolutionary history of species
What is a species?
organisms that can mate and produce living and fertile offspring
Reproductive Isolation
when two organisms do not mate together
what would prevent two organisms from mating?
prezygotic barriers (attempt to mate but wont happen)
Prezygotic barriers
T → Temporal Isolation (Different mating times)
B → Behavioral Isolation (Different courtship behaviors)
H → Habitat Isolation (Different environments)
T → Temporal Isolation (Different mating seasons/times)
M → Mechanical Isolation (Physical incompatibility)
G → Gametic Isolation (Sperm & egg don’t fuse)
H → Geographical Isolation (Separated by physical barriers like mountains or rivers)
Acrynom for prezygotic barriers
The big happy tigers make great homes
Post Zygotic
1) reduced hybrid fertility
2) reduced hybrid viability
3) hybrid breakdown
Geographical Isolation
organisms are geographically isolated in different organisms
- mutatiosn evolve independently
Habitat Isolation
organisms live in seperate habitats
Behavioral Isolation
courtship or mating rituals
Temporal Isolation
time (seasons, time of day, time of breeding season)
Gametic Isolation
sperm and egg cannot unit to form a zygote
Mechanical Isolation
physical barriers to reproduce (ex. girafee and pig)
Allopatric Speciation
organisms that were together seperate and speciate (all over the world)
Sympatric Speciation
species in the same region speciate (habitat isolation)
Hybrid Breakdown
F1 is fertile but F2 is not
Artifical Selection
humans selecting for desirable traits in future populations
Selective Pressure & Antibiotic Resistance (Positive Selection)
Antibiotic resistance occurs due to positive selective pressure, where bacteria with resistance genes survive and reproduce, while non-resistant ones die.
Selective Pressure & Genetic Diseases (Negative Selection)
Negative selective pressure eliminates traits that reduce survival or reproduction.
Whats common betwwen natural selection and artifical selection?
changes in phenotypes overtime
