EXAM 1 Study Deck Flashcards
What is Darwin’s theory of Descent with Modification
Darwin’s theory is that different species share characteristics because they evolved from a single ancestor.
descent with modification
Individuals do no evolve, but populations evolve over time. Depending on an individuals relative fitness some will reproduce more than others causing…….
Accumulation of favorable characteristics in a population over time.
unequal ability to survive and reproduce means accumulation of favorable traits over generations.
descent with modification
If more young are born than can survive then…
they will compete for limited resources.
What three things are required for Natural Selection?
1)
2)
3)
1) Individuals must vary in characteristics
2) Traits must be heredible
3) Individuals must differ in relative fitness in a particular environment.
Where does variation come from?
1) sexual reproduction
2) error during meiosis
3) mutation
4) gene duplication
5) Gene flow
Define a phenotype
A phenotype is a physical expression of a gene.
Why cant selection produce perfect adaptions?
Because selection can only use what is already provided. It cannot CREATE variation.
Environment and relative fitness determines which individuals survive and pass down characteristics.
What is meant by the Agent of Selection
Relative fitness depends on the environment, the same phenotype may have differing fitness in certain environments.
Define Genetic Drift
Genetic drift is the random fluctuations in allele frequency, randomly eliminating genotypes and decreasing variation.
In large populations this balances out, not so much in smaller ones.
The Bottleneck effect
The bottleneck effect is when a population decreases dramatically. As result of genetic drift
The Founder effect
A large population arises from a small one. Leads to limited diversity and low ability to respond to environmental change, fixation of allele (bad if negative ones).
What forces keep variation despite genetic drift.
sources of variation
Mutations-neutral or positive
Sex (recombination)-horizontal gene transfer
Crossing over/independent assortment
Gene duplication
Gene Flow-mitigation in/out of population
How does speciation happen?
1)
2)
1) Gene flow must be interrupted between populations of the same species.
2) Populations diverge sufficiently becoming reproductively isolated
Allopatric Speciation
Populations become physically isolated geographically. by mountains, rivers, distance, islands.
Sympatric Speciation
subpopulations share the same location but become reproductively isolated because they access new food supplied, go to different regions or interbreed with others.
Define Species
Species are reproductively isolated from others. No hybrids thanks to isolating mechanisms.
Isolating mechanisms preventing hybrids form forming: PRE-ZYGOTIC
Habitat/Temporal/Behavioral isolation
Prevents fertilization in the first place
Individuals don’t recognize or come into contact with each other. Mating rituals don’t match up/mate at different times.
Isolating mechanisms preventing hybrids form forming: PRE-ZYGOTIC
Mechanical Isolation
Prevents fertilization in the first place
“Lock and Key don’t fit”
Sperm cant reach eggs, mating unsuccessful
Isolating mechanisms preventing hybrids form forming: PRE-ZYGOTIC
Gametic Isolation
Prevents fertilization in the first place
Sperm reaches eggs, but fertilization doesn’t occur.
Isolating mechanisms preventing hybrids form forming: POST-ZYGOTIC
Hybrids dont survive
Hybrids have low viability and fertility
Most common. Inivitable
Isolating mechanisms preventing hybrids form forming: POST-ZYGOTIC
Hybrids are Sterile
Hybrids have low viability and fertility
Reduced hybrid fertility
Isolating mechanisms preventing hybrids form forming: POST-ZYGOTIC
Hybrids have low fitness
Hybrids have low viability and fertility
They may be viable or fertile but their offspring may be sterile or have low reproductive success of survival.
What is Upwelling and how does it occur
Upwelling is when lower level waters, colder but filled with nutrients, come up to the surface. Usually as a result of strong offshore winds. Breaks up the Thermocline layers. It introduces more nutrients to the surface helping growth of organisms and brings more species in for food.
Coriolis effect
Air moves clock-wise in the northern hemisphere and counter-clock-wise in the southern hemisphere.
Air currents are the result of the coriolis effect and rising warm water.
Thermoclines
The colder (denser) waters of the ocean are beneath the warmer surface waters
Haloclines
The saltier and more nutrient rich (denser) materials are in the lower water levels, while less on the top surface levels.
Colder water also holds more oxygen than warm surface waters.
Primary productivity is the lower level creatures in the food chain reproducing and growing, providing food for the higher level creatures.
What affects Primary productivity?
Primary productivity can be limited by nutrients such as Nitrogen and Phosphorous.
Aquatic productivity is limited by light-half absorbed on the surface, only 5-10% reaches 75%lower levels
What is El Nino and how does it affect primary productivity?
EL Nino is when air pressure decreases in the eastern pacific, allowing warm water to flow eastward.
This decreases upwelling, limiting primary productivity
Tropic levels
The tropic levels are the levels of the food web
Primary producers(phototrophs)=> Primary consumers(herbivores)=>Secondary consumers(carnivores)
Define foodchain
the food chain is the transfer of energy between the different trophic levels.
How many links can be made in the trophic level
limited to 5 links at most
trophic interactions
Bottom-Up
biomass at lower levels affect higher levels
nutrients-producers-primary consumers-secondary consumer
trophic interactions
Top-Down
higher trophic level limits abundance of lower trophic level
-many species feed at multiple trophic levels
sec consumer-primary-producers-nutrients
biomass
combines mass of all individuals
food web
food chains all linked together-complex trophic interaction
common prey species for marine birds and mammals
phytoplankton-algae,cyanobacteria,diatoms,dinoflagellates
(primary producer)
zoo plankton- copepods, fish larva, eggs(Primary consumer)
fish- anchovy,sardine,herring,rockfish,salmon,capelin (Secondary consumer)