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