Ecology Lesson 2

Question 1

Population Density can do what?

Answer 1

Affect birth and death rates. No population can grow forever because not enough space/resources. The density tells us how many people are fighting for the same resources.

Question 2

Sea Otters

Answer 2

Live in groups and very social. Forage (look for food) alone but sleep/rest together. Young nursed and carried by mother for 4 to 8 months, mother care a lot for baby. Found on pacific coast. They use kelp to stay in places. Vert smart. They use tools like rocks to get things open and to get things off the sea floor.

Question 3

What do sea otters feed on?

Answer 3

Urchins, clams, snails, crabs, fish.

Question 4

Sea Otter former and present-day range?

Answer 4

Used to have a lot of otters but the population shrunk and some went extinct and had to be re-introduced.

Question 5

How did the otter population decrease?

Answer 5

When the europeans arrived the fur traded happened (1700s to 1911). There is a lot of money in it, the less otters more expansive fur is because it’s rare. From 100 000 to 2000. Then in 1911 the harvest moratorium was signed (an agreement to stop hunting them). The last otter in BC in 1929, where it had to be re-introducted or translocation.

Question 6

Amchitka Island

Answer 6

Very remote, part of US where war combat occurred (1940s). They was lots of otters there. Then in 1947 there was a wildlife refuge as a lot of otters were there. In 1950s it was proposed for nuclear testing and they move the sea otters to BC because they use to live there.

Question 7

The translocation of otters to BC?

Answer 7

There was a high mortality in moving them. Most translocations from 1965 to 1972. But the 90 otters were introduced to Vancouver island.

Question 8

Otters in BC

Answer 8

Because of the unconstrictied environment and there was no other otters there, there was exponential growth from 1977 to 1995. r=0.19. Then the growth rate slowed to r=0.08.

Question 9

Why did the otter grow rate slowed?

Answer 9

Resources become limited, Food & space, Sea otters compete for food. Because of the increased amount of sea otters (aka intra-specific).

Question 10

Intra-specific competition

Answer 10

Competition for resources among
individuals of the same species.

Question 11

Carrying capacity (K)

Answer 11

The number of individuals of a population that an environment can support. The limit.

Question 12

What does the K for otters depend on?

Answer 12

Length of coastline
Suitable habitat
Suitable food

Question 13

Birth rate of sea otters?

Answer 13

Per capita birth rate doesn’t vary
with density. Birth rate is density independent. Still have the same number if pups no matter how many there are.

Question 14

Death rates of sea otters?

Answer 14

Thin mothers: pups don’t survive. Pup death rate increases with density. Pup death rate is density-dependent. Can’t invest as much into each pup.

Question 15

Equilibrium Density

Answer 15

Equilibrium if birth rate (b) = death rate (d) (aka carrying capacity). b>d is r>0. b<d is r<0.

Question 16

Density-dependent regulation

Answer 16

The density the number of individuals is regulating the population size itself.

Question 17

Regulated population

Answer 17

Returns to equilibrium. At least one density-dependent rate.

Question 18

Limits to population growth?

Answer 18

Growth slows as resources become
less abundant. This is because birth rates decline and/or death rates increase. Density-dependent birth or death rates regulate populations around an equilibrium.

Question 19

Logistic growth model equation

Answer 19

dN/dt = rN (K-N)/K
(K-N)/K will stop the population from going infinity. It’s sigmoidal form.

Question 20

If N is small relative to K (small population size)?

Answer 20

The population is close to exponential.

Question 21

If N equals K (i.e. population is at carrying capacity)?

Answer 21

Population growth is 0.

Question 22

If N is larger than K (i.e. population is above carrying capacity)?

Answer 22

The population growth is negative.

Question 23

Carrying capacity in real populations?

Answer 23

Population fluctuates around K. Density-dependence not perfect. Environment changes, there is disease, boom in regulation. (ie. wolf-moose impact each other and it’s predator-prey).

Question 24

When does population growth slow?

Answer 24

As the population approaches K.

Question 25

Life history strategies

Answer 25

The best way to pass on the genes. ie. sea urchins have several million eggs per year, while sea otters have 1 pup per year. There is no perfect strategy it depends in context and environment and other species.

Question 26

Why such huge differences in life history strategies?

Answer 26

Maximizing fitness: maximizing contribution to the gene pool of the next generation.

Question 27

Reproduction involves trade-offs

Answer 27

More offspring -> less energy put into each one (less hardy, resilient, and mortality is likely to higher). Energy includes offspring size, parental care. Larger offspring with more parental care are more likely to survive. (tougher well nourished).T

Question 28

Trade-Off

Answer 28

Many low quality (most do not survive). Few high quality (each likely to survive). Different organisms take different route for this.

Question 29

r-strategy

Answer 29

Maximize number of offspring. Smaller offspring. No parental care.

Question 30

K-strategy

Answer 30

Maximize offspring survival. Larger offspring. Parental care.

Question 31

Advantage of strategy depends on what?

Answer 31

The environment, why one isn't exactly better than the other.

Question 32

r-strategy advantageous where quality matters little, like?

Answer 32

Physically harsh environments. Unpredictable environments. Most offspring will not survive anyway.

Question 33

K-strategy advantageous where quality matters a lot, like?

Answer 33

Highly competitive environments, Predictable environments, Stronger more likely to survive, Provisioning/care increases survival.

Question 34

r-strategists are in what kind of habitats?

Answer 34

Open / disturbed - Roadsides, lava flows Temporary - Tiny ponds, cropland Unpredictable - Deserts (rain), grasslands (fire)

Question 35

K-strategists are in what kind of habitats?

Answer 35

Permanent - Rainforest, open ocean, large lakes Resource limited - Or crowded etc

Question 36

r-strategists tend to be?

Answer 36

Invading and colonizing species.

Question 37

K-strategists tend to be?

Answer 37

Strong competitors

Question 38

Life history strategies Evolved through natural selection & differences in?

Answer 38

Environment, Population density (competition for resources), Availability of mates (sex ratio).

Question 39

r-strategy: death rate varies with age (how?)

Answer 39

Most young die – low survival. But adults often live a long time – high survival.

Question 40

Differences in r and K strategy survivability?

Answer 40

r-strategy: young is low, adults is higher. K-strategy: young is higher, adults is low very late in life. (shown by survivorship curves)

Question 41

Cohort method

Answer 41

Follows a group of individuals organisms or population of a species through time. It records there amount that are alive.

Question 42

Types of survivorship curves

Answer 42

Type I: K-strategist. Produce few offspring, most survive. Type II: A mix of both. Type III: r-strategist. Produce many offspring, most die.

Question 43

Mortality varies based on what?

Answer 43

How old you are and life history strategy.

Question 44

Demography

Answer 44

Studying the affects of population age structure and population growth. They can infer what's happening in human populations around the world.

Question 45

Global population age structure pyramid

Answer 45

Divided by sex. Narrow when get older, and wide when young.

Question 46

Canada pyramid

Answer 46

Wide at the boomers because more birth rate from more resources. Echo also a little wide (children of boomers). Birth rates declining. 0 – 4 years: males > females. 75+ years: females > males.

Question 47

Death rates vary with age

Answer 47

High when baby, then drops a lot, then increases as gets older. Higher mortality for men. A 45 year-old is more than twice as likely to die as a 25-year old. 25 year-old male is ~3 times as likely to die as a 25-year old female.

Question 48

Birth rate varies with age

Answer 48

30-34 is where births is highest. Used to be 10 years early but changed because education and resources.

Question 49

Births and deaths vary over time in Canada

Answer 49

Both births and deaths have decreased.

Question 50

Canada and Chine population pyramid

Answer 50

Both have Spindle shape: Boomer bulge, Echo generation in their late 20s, Large decline in birth rate in recent years.

Question 51

Differences in population in countries?

Answer 51

Because difference in when people have kids, how many, and the opportunities they have.

Question 52

Niger population

Answer 52

Little decline in birth rate. High death rate – concave shape.

Question 53

India population

Answer 53

Birth rate declining. Lower death rate – convex shape.

Question 54

How high is human population growth?

Answer 54

8.2 billion, became every high in 2000s. Global population growth rate expected to continue to decline. Uncertainty in how many people there will be.

Question 55

Total fertility rate (TFR)

Answer 55

Number of children per female over their lifetime.

Question 56

Replacement TFR

Answer 56

2.1 children. At this TFR, births exactly replace deaths. Zero population growth. 0.1 because some kids die and some women chose not to have kids.

Question 57

TFR in World and Canada?

Answer 57

Both decreasing. While Canada's is less than 2.1, the population is still growing because of immigration.

Question 58

Population inertia

Answer 58

A cohort of people who are of reproductive age still going to get these bulges and the cohort works it's way through the population. This means the population weeps growing even when TFR is below 2.1. ie. in china, population kept growing because of age structure.

Question 59

World population growth?

Answer 59

The world’s population is still growing, but rate of growth is declining. Birth rates have declined in most countries, and many are at or below replacement fertility. Age structure affects population growth. Young populations keep growing for a time after they reach replacement TFR.