Caused by resources being consumed; population levels too high
Logistic growth: graph that shows steady increase followed by flattened line (carrying capacity) which may or may not then lead to a drop
Evidence for Evolution:
Fossil records
Comparative anatomy - homologous structures
Comparative embryology - similarity in embryos between species
Molecular biology
Biogeography - similarity of species
Natural Selection:
Natural process
Requires 100,000 yrs to occur
Wolf-like:
↳Wolf
↳Coyote
↳Fox
↳Dog
Artificial Selection:
Humans serve as the environment
Requires 1,000 yrs to occur
Examples:
Dog breeds
Cat breeds
Cattle breeds
Plants
Types of genetic drift:
Bottleneck Effect
Founder Effect
Bottleneck effect
hunters kill genetic diversity
Founder effect
a few leave population and start new population
Gene flow
Isolated population; no migration
Microevolution
Is the change in allele frequencies that occurs over time within a population.
Microevolution is due to four different processes:
Mutation, selection (natural and artificial), gene flow, and genetic drift.
Types of natural selection:
Stabilizing
Directional
Disruptive
Stabilizing natural selection
favors intermediates (the average)
Directional natural selection
Favors one extreme (light vs dark)
Most common
Disruptive natural selection
favors two extremes
diversifying
Peppered Moth
Smog from industrial revolution caused directional selection
dark survived, light were killed
Hardy-Weinberg Law
A principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors. When mating is random in a large population with no disruptive circumstances, the law predicts that both genotype and allele frequencies will remain constant because they are in equilibrium.
Hardy-Weinberg Law assumes:
Large population
No natural selection
No mutation
Random mating
No gene flow
No genetic drift
Hardy-Weinberg equation:
p+q=1
P: Dominate gene
q: Recessive gene
Reproduction Barrier - Pre-zygotic:
Temporal - time
Habitat
Mechanical - plants pollinated by birds
Behavioral - mating rituals
Gametic - sex cells incompatible (eggs/sperm)
Reproductive Barriers - Post-zygotic:
Hybrid sterility
Hybrid inviability - aborts
Hybrid breakdown - f1 ok, f2 breaks down (sterile)
Hybrid animals:
Mule - sterile
Liger - female not sterile
Leopon
Cama - llama + camel
Zorse
Wholphin
Types of Speciation:
Allopatril - due to geography
Sympatril - due to complete nondisjunction (polyploid)
Adaptive radiation - traveling
Allopatril speciation
due to geography
Sympatril speciation
due to complete nondisjunction (polyploid)
Adaptive radiation
Species travel from different locations and turns into new species
Birds w/ correct adaptations survive
Polypliody
Polyploid cells and organisms are those containing more than two paired (homologous) sets of chromosomes. Most species whose cells have nuclei (Eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent.
Gradualist Theory of Evolution
Changes occur slowly
Punctuated Theory of Evolution
Changes occur quickly
Properties of a biological community:
Species diversity
Type of vegetation
Stability - how fast does it recover from disaster
Trophic structures - feeding levels
Trophic Structure:
Quaternary Consumer (hawk)
⇑⇑⇑⇑⇑
Tertiary Consumer (snakes)
⇑⇑⇑⇑⇑
Secondary Consumer (frogs)
⇑⇑⇑⇑⇑
Primary Consumer (insects)
⇑⇑⇑⇑⇑
Producer (plants)
Niche
The specific area where an organism inhabits.
Niche - Competitive Exclusion
+ Examples
No 2 species can occupy the same niche
Examples;
Paramecia
Dingo vs. Thylacine
Homo Neaderthalensis vs. Homo Sapiens
Ecological Relationships:
Parasitism
Commensalism
Mutualism
Parasitism
One benefits; Other is harmed
Examples:
Leeches
Tapeworm
Plasmodium (malaria)
Ticks
Commensalism
One benefits; other is unaffected
Examples:
Shark/Remora
Mutualism
Both benefit
Examples:
Ant/Acacia
Flower/Bird
Keystone Predator
Maintains ecosystem
Examples:
Starfish
w/ starfish 16 species of shell fish w/o 1 species
Wolf
regulates Elk population in Yellowstone park w/o wolf little vegetation left