Populations Flashcards
What is a population?
- Members of the same species living in the same area at the same time
- classified in two ways: open,closed
What is an open population?
- Population that us impacted by birth, death, immigration, emegration
- (things move in and out, which may effect levels)
What is a closed population?
- A population affected by birth and death only
- ie: fish in pond (can not leave or enter)
What is the objective of reproductive strategies?
To maintain a stable population
What is an R-selected reproductive strategist?
Characteristics: Smaller organisms short life spans early reproductive age high reproductive rate many offspring at a time offspring grow rapidly no parental care
ex: bacteria, insects, fish
What are some benefits of an r selected reproductive strategist?
- restores populations quickly
- increases chance if survival for some offspring
- adapts quickly (due to large numbers, certain individuals with certain characteristics will survive and pass it on in large numbers)
What is a K-selected reproductive strategist?
Characteristics:
- larger organisms
- longer life spans
- later reproductive age
- lower reproductive rate (less frequent)
- fewer offspring
- offspring grow slower
- have parental care
ex: bears, humans, elephants, (mammals)
What are the pros of K-selected reproductive strategists?
- genetic variation
- higher survival rate of offspring
Which factors affect population size?
- biotic potential - factors that increase population size
- environmental resistance- biotic+abiotic factors that decrease population size
What is biotic potential and the types?
-factors that increase size
a) birth potential-number of offspring per reproductive cycle
b) capacity for survival
c) breeding frequency- # of times species reproduces per year
d) length of reproductive life- age that they start reproducing
What is environmental resistance and its limting factors?
-factors that decrease population size
Limiting factors
a) density dependant limiting factors
- factors that depend on the number of individuals living within one area
ie: amount of food/water, disease, shelter, mates, predators, etc
b) density independent limiting factors
- factors that are do not depend on the number of individuals within an area
ie: wildfire, flooding, natural disasters, human activity
What are the two types of population curves?
1) J curve
2) S curve
What is the J-curve?
- An exponential curve
- r selected organisms
- at the highest biotic potential
- once it reaches the peak, it ‘crashes’ (runs out of resources to maintain the popuation)
- humans have not yet reached ‘crash’ point
What is the S-curve?
- logistic curve
- k- selected organisms
1. lag phase -highest biotic potential, lowest environmental resistance
2. growth phase- exponential growth, decreasing biotic potential, increasing environmental resistance
3. stationary phase - reach carrying capacity, max environmental resistance, lowest biotic potential
4. death phase- resources deplete, decrease in population, increased biotic potential, decreased environmental resistance
What is a community?
-more than one population living in the same area
What are the types of interactions within a community?
1) competition
2) predation
3) symbiotic relationships
What is competition?
-Gause’s principle suggests that when two species occupy the same niche, one will be eliminated
2 types of competition:
a) intraspecific- competition that exists within the same species ie: food, mates
b) interspecific- competition that exists between species ie: food, living space
What is niche diversification?
- two species slightly alter their niche to decrease competition
What is predation?
-predator/prey relationship
2 ways to AVOID predation:
a) camouflage- adaptations that hide an organism from anither
b) mimicry- when an organism takes on a characteristic of another that gives it a survivial advantage (scares predator into thinking the prey is dangerous due to its similarity to actual dangerous organisms)
What are symbiotic relationships?
-3 types of close relationship between organisms
a) parasitic- 1 benefits, 1 harmed
b) mutualism- both benefit
c) commensalism- 1 benefits, 1 unaffected
What is succession?
- How ecosystems change+recover from damage
- impacted by abiotic+biotic factors
What is a pioneer species?
- first plants/animals that appear in succession
- small/simple
ie: lichen, moss, insects
What is the climax community?
- at the end of succession
- dominated by one large organism, less biodiverse ie: pine trees
What are the two types of succession?
- Primary succession
- returns to climax community after total destruction (soil has been removed), takes a long time
- ex: volcanic eruption - Secondary succession
- return to climax community after partial destruction, soil has NOT been removed
ex: forest fire, tsunami, tornado, landslide (natural disasters)
What is the Hardy weinberg principle?
States that frequencies of alleles in a population will remain constant over generations if 5 factors are met
What are the 5 factors of the hardy weinberg principle?
- population is very large
- no migration occurs
- no mutations occur
- no natural selection
- Random mating
What occurs when these 5 factors are NOT met?
Evolution will occur
What is the formula for the Hardy-Weinberg principle? (if all of these factors are met the population can be calculated)
p^2+2pq+q^2 = 1
h
p= one dominant allele q= one recessive allele
p^2= both dominant alleles q^2= both recessive alleles 2pq= heterozygous
Usually find q^2 first to solve the rest. Often the dominant allele is present, which offers two options and you must find q, which has only the recessive option available, to find the population values.
Which factors must occur for the Hardy-Weinberg principle to not apply?
- Natural selection
- Non-random mating
- mutation
- genetic drift
- Gene flow
What is natural selection?
Mutation gives survival advantages to an organism
What is non random mating?
Many organisms choose a mate based on certain characteristics
What is mutation?
Changes to DNA that can be inherited
What is genetic drift?
A shift in the gene pool based on events ie: change in frequency of alleles
2 ways this occurs:
a) bottle neck effect
b) Founder’s effect
What is the bottleneck effect?
A sudden, dramatic reduction in population size. Random ex: natural disasters
- variability of alleles decreases, surviving organisms restart population
- those left=right place, right time
What is the Founder’s effect?
Small group moves away from the larger population, makes new colony
ex: amish, finches in galapagos
Both forms of genetic drift decrease genetic variability
What is gene flow?
-genes move out of a population due to migration
immigration=increased variability
emmigration=decreased variability
What are the 4 population dynamics formulas?
- population density (how many per 1 unit of area)
- Change in population (how much a population has increased or decreased)
- population growth rate (how much it increases or decreases within a period)
- Growth rate per capita
What is the population density formula?
d= N (original .population size) / A (area)
What is the population change formula?
delta N = (natality+immigration) - (mortality+emmigration)
ie: (factors that increase population size) - (factors that decrease population size)
What is the population growth rate formula?
gr (growth rate) = delta N (change in population) / delta t (change in time)
What is the formula for per capita growth rate?
cgr (capita growth rate) = delta N (change in population) / N (original population size)
