UNIT 1: Population Ecology

Question 1

Define “Ecology”.

Answer 1

Scientific study of interactions that determine the distribution and abundance of organisms.

Question 2

What are the 2 main types of interactions?

Answer 2

1. Abiotic (physical)

2. Biotic (biological)

Question 3

Define distribution and abundance.

Answer 3

Distribution: geographical area
Abundance: how many organisms/unit area

Question 4

Define the 2 types of interactions.

Answer 4

1. Abiotic (physical): non-living part of an ecosystem that shapes its environment
   ex: temperature, water availability, weather, light, pH.
2. Biotic (biological): living organism/pair of living organisms living together that shape their environment
   ex: parasitism, predation, competition.

Question 5

Define “population”.

Answer 5

Group of interbreeding individuals.

Question 6

What are the main characteristics of a population and what do they mean?

Answer 6

1. Size (N): number of individuals
2. Age structure: reproductive cycle, growth rate, males and females
3. Density (N/unit area)
4. Distribution: geographical area/range
5. Dispersal: depends on scale (small or large), 3 patterns possible (clumped, regular, random)

Question 7

How is the density of a population of larger individuals affected?

Answer 7

Low density, because the individuals need more space, more energy and more resources to grow, so there are fewer/unit area.

Question 8

What are the 3 possibilities of growth rate and their effect on size of population?

Answer 8

Zero = consistent N
Negative = decreasing N
Rapid = increasing N

Question 9

What is the equation for growth?

Answer 9

G = (births+imm) - (deaths+emi) / time

Question 10

What are the 2 types of growth?

Answer 10

1. Exponential: grows exponentially, first with lag phase (b ~ d) and then max growth phase ( b&raquo_space;> d).
2. Sigmoid (logistic): slow increase until N approaches K (carrying capacity), and then no more growth, pop becomes consistent because of limiting factors.

Question 11

How can a population realize its biotic potential (maximum growth)?

Answer 11

• Maximize natality: min age of sexual maturity, max fecundity, max length of reproductive life, min pregnancy length
• Minimize mortality: death at old age

Question 12

What are the most important limiting factors that impacts a population’s growth and carrying capacity

Answer 12

• Weather
• Food (competition for food)
• Presence of other individuals (predation)
• Space (competition)

Question 13

Define carrying capacity (K).

Answer 13

Maximum N that the environment can support based on conditions at a given time and place.

Question 14

After a really high growth phase, a population will eather gain a new K, but more often it will crash. Define a population crash and why it happens.

Answer 14

Happens when pop reproduces really quickly, so slope keeps going up until limiting factors inhibit further growth, and even decreases drastically the N.
ex: diseases, weather, resources (food), competition.

Question 15

Give an example of a population crash with an opportunistic sp.

Answer 15

An opportunistic sp will reproduce very quickly when there is an opportunistic environment (mosquitoes in hot and humid weather during the summer), and then all die once the environment changes (mosquitoes all die when it gets colder and dryier)

Question 16

Explain and give example of a pop growth curve involving 2 dependent spp.

Answer 16

The dynamic of predator/prey leads to pop growth curve that are similar where 1 is dependent of the other, can lead to 2 pop crashes.
Ex: flowers (prey) and bees (predator), when many flowers, there are many bees, but if because of abiotic factor flowers die, more bees will die too.

Question 17

What are density-dependent factors?

Answer 17

Factors influenced by pop density

• effects are more severe when N ↑
• effects are less severe when N ↓

ex: covid spreads more if there are more indivduals

Question 18

What are exemples of density-dependent interactions?

Answer 18

Competition, predation, parasitism.

Question 19

Describe density-dependent competition.

Answer 19

Use of a limited resource by 2 or more individuals.
(-/-): both species are losers, they both get less than if they were alone.

1) Interspecific : ↔ different spp
2) Intraspecific: within same sp

Question 20

Describe density-dependent predation.

Answer 20

Act of 1 organism killing and eating another (predator-prey)

(+/-): predator gains food, prey gets killed

Question 21

Describe density-dependent parasitism.

Answer 21

1 organism lives in/on another, harming it.

(+/-): one gains and feeds on an organism, while the other is harmed.

Question 22

Which type of competition plays a bigger role on pop size regulation?

Answer 22

Intraspecific

ex: kangoroo fighting
ex: deer pop is high = ↑ competition, ↓ quality food, ↓ ovulation, ↓ energy of females to reproduce = ↓ pop size.

Question 23

The prickly pear cactus has no predator, so it just keeps growing and is invading too many areas. What can be done to regulate the population?

Answer 23

PREDATION! Introduce a caterpillar that’s only food is prickly pear cactus to decrease the cactus’ pop size.

Question 24

Give an example of parasitism to explain why one gains and one loses.

Answer 24

Parasites on the skin of a fox, they eat away its fur and skin, so the parasites pop keep growing, while the fox pop is infected.

Question 25

What are the density-independent factors?

Answer 25

The abiotic factors (physical), where severity does not change (↑ or ↓) with population density.

Question 26

Define life history patterns and give examples.

Answer 26

Programmed life events from birth, to reproduction, and to death.
Examples:
-Life tables
-Survivorship curves (survivorship and reproduction)

Question 27

Define the main variables for life tables.

Answer 27

Lx: # individuals alive

dx: # individuals dying
qx: mortality rate
px: survivorship rate

Question 28

What are the 3 types of survivorship curves?

Answer 28

1. High survival rate until late lifespam
   - large mammals, ↑ parental care, ↓ # offsprings
2. Constant mortality rate
   - small mammals, amphibians, reptiles, ↓ parental care, medium # offsprings
3. High juvenile mortality (then low adulthood mortality)
   - fish, plants, insects, corals, NO parental care, ↑↑↑ # offsprings

Question 29

Why do humans reach maximum growth phase faster than other animals?

Answer 29

1. Ability to put aside many limiting factors
   
   • medecine
   • sanitation (hygiene)
   • new energy sources (technology)
2. Ability to ↑ K in our env.
   
   • agriculture
   • domestication of animals (↑ food)
3. Ability to expand into new habitats & climates (adaptative skills)

Question 30

Human population: define demographics.

Answer 30

Vital statistics of human pop:

• size
• density
• age structure
• distribution

Question 31

Human population: describe age structure.

Answer 31

• Developping countries: ↑↑↑ growth rate

- Educated countries: ~ growth rate

Question 32

Why is resource consumption a good factor to consider in growth?

Answer 32

It is a good indicator of the future of most animal population.

Question 33

What distribution factor would you expect for black bear in North America?

Answer 33

Clumped: because of large scale and abiotic factors

Question 34

What is required to maximize a pop’s biotic potential (growth)?

Answer 34

• low sexual reproduction costs

- non-limiting environmental resources

Question 35

On a small scale, which factors mostly impact the individual’s distribution?

Answer 35

Biotic and/or Abiotic factors.

Question 36

Which survirvorship curve exhibitis the lowest adulthood mortality rate?

Answer 36

High juvenile mortality.