6.6.2 interactions between populations

Question 1

interspecific competition

Answer 1

competition between individuals of different species

Question 2

intraspecific competition

Answer 2

competition between individuals of same species

Question 3

predator

Answer 3

hunts other animals (prey) for food

Question 4

what can act as a limiting factor on prey’s population size

Answer 4

predation

Question 5

list the relationship between a population of a predator & it’s prey (1-5)

Answer 5

1. predator population increase = more prey eaten
2. prey population decreases = less food for predators
3. less food = fewer predators survive & population size decreases
4. fewer predators = fewer prey eaten & population size increases
5. more prey = predator population size increase

..CYCLE REPEATS

Question 6

what happens when the intensity of competition in an ecosystem increases

Answer 6

• rate of reproduction decreases as fewer organisms have enough resources to reproduce
• death rate increases as fewer organisms have enough resources to survive

Question 7

result of intraspecific competition

Answer 7

• slows pop. growth as resources become limited & individuals compete
• those not well adapted fail to reproduce & die
• pop. enters stationary phase

Question 8

how does intraspecific competition keep population size relatively stable

Answer 8

• if pop. size drops, competition reduces & population size increases
• if pop. size increases,competition increases & pop. size drops

Question 9

what 2 things can interspecific competition affect

Answer 9

1. population size of a species
2. distribution of species in an ecosystem

Question 10

russian scientist who carried out work on interspecific competition

Answer 10

Gause in 1934

Question 11

what did Gause do

Answer 11

• grew 2 species of paramecium separately & together
• together = competition for food
• over 20 days, p.caudatum died out until p.aurelia pop. increased & only species remaining

Question 12

which paramecium obtained food more effectively when grown together (Gause)

Answer 12

p.aurelia (over p.caudatum)

Question 13

what did Gause conclude

Answer 13

• more overlap between 2 species niches means more intense competition
• if 2 species have exact same niche, 1 is out-competed by the other & dies out/becomes extinct in habitat

Question 14

competitive exclusion principle

Answer 14

2 species cannot occupy same niche & if do, 1 dies out/becomes extinct in habitat
- more overlap of niches = more intense competition
- used to explain why certain species only grow in certain places

Question 15

instead of extinction, what can interspecific competition result in

Answer 15

one pop being much smaller than the other & both sizes remaining relatively consistent

Question 16

laboratory v. wild - interspecific competition

Answer 16

lab = easy to exclude effects of other variables, so habitat of 2 species remains stable

wild = wide range of variables may act as limiting factors for growth of diff. populations & may change daily