lecture 2 ecology

Question 1

population density – what does it effect

Answer 1

affects brith and death rate

Question 2

sea otters

Answer 2

live in groups, look for food individually but sleep/rest together, heavy maternal investment – young is nursed and carried for 4-8 months.

Question 3

what happened to sea otters

Answer 3

there is now gaps in distribution.
all startted in early 1700’s-1911 – this was the fur trade – europeans arrived, and population decreassed from 100,000 to 1000-2000

in 1911 an agreement was signed to limit/stop harvesting (harvest moratorium) – this was a bit too late for specific popultion as the last otter in BC was driven to extinction in 1929.

Question 4

what did we do to fix this extinction of otters (think about process, where, why it didnt work)

Answer 4

currently there is a population of otters in BC, but how?

translocation/reintroduced.
otters were moved from one place to another to try to reestablish a population that has been driven extinct.

in 1947 – Amchitka land was made into a wildlife refuge for tters as it was a very remote land – that didnt last – 1950s the land was proposted to be suitable for nuclear testing, so otters were moved to BC where there had been ottewrs in the past. – this was good, there was no competition between other otters, but growth rate soon slowed because of more competition, food and space, and resourced ultimately became limited.

Question 5

carrying capactiy

Answer 5

number of individuals of a population that an environment can support

Question 6

what happens as the number of sea otters increase

Answer 6

less food – lower population growth rate (r)

Question 7

what do we look at to determine the birth and death rates of sea otters

Answer 7

we look at density dependent births and deaths

Question 8

birth rates in otters

Answer 8

the birth rate in otters is density-independent, meaning the birthrate does not depend on the number of individuals in the population

Question 9

death rates in otters

Answer 9

the death rate is density dependent. this means that the death rate is dependent on the number of individuals in the population. this could mean limited space, resources, and an increase in competition for food. whixh leads to the mothers investing less in their pups, starvation..

Question 10

equilibrium density

Answer 10

if birth rate equals death rate – will be the intersection of both lines.

Question 11

density dependent regulation

Answer 11

factors that influence population size based on the population density. in other words, basically density is regulating population size.

Question 12

regulated population – what is needed.

Answer 12

at least one density dependent rate – this returns population to equilibrium

Question 13

limits to population growth – summary

Answer 13

growth slows as resources become less abundant, this is because birth rates decline and/or death rates increase. density dependent births or death rates regulate populations around an equilibrium

Question 14

Modeling density dependent growth – equation

Answer 14

the logistic growth model
dN/dt = rN(K-N/K)

Question 15

if N is smaller than K (logistic growth)

Answer 15

if N is small relative to k, carrying capacity is fixed (1) – population growth is CLOSE to exponential

Question 16

if N = K (logistic growth)

Answer 16

population will be at carrying capacity, the growth will be constant

Question 17

If N is larger than K (logistic)

Answer 17

population will be above carrying capacity, population growth will be negative

Question 18

carrying capacity in real populations

Answer 18

population fluctuates arounddd K, it is never perfectly stable – there are still some things in the environment (predators, disease, environment changes)

Question 19

Life history changes urchins vs otters

Answer 19

urchins – several million eggs per year
otters – 1 pup per year

Question 20

life history strategies

Answer 20

maximizing fitness, the contribution to the gene pool of the next generation. – doesnt necessarily mean maximizing number of offspring

Question 21

reproduction tradeoffs

Answer 21

low vs high quality
low – most do not survive
high – all likely to survive

Question 22

different strategies

Answer 22

depend on environment and ecosystem (k and r)

Question 23

k strategy characteristics

Answer 23

carrying capacity, maximize offspring survival, larger offspring, parental care.

– quality of offspring matters a lot, highly competitive environment, predictable environments, stronger, more likely to survive, parental care increases survival.

Question 24

r strategy characteristics

Answer 24

maximumizing growth of population, max number of offspring, smaller offspring, no parental care.

– advantage where quality of offspring matters very little, physically harsh environments, unpredictable environments, most offspring will not survive anyway

Question 25

organisms of r strategies tend to be found in habitats that arE:

Answer 25

ope/disturbed -- roadsides, lava flows. temporary -- tiny ponds, cropland unpredictable -- deserts (rain), grasslands (fire) the organisms tend to be invading species, colonizing species

Question 26

organisms of k strategies tend to be found in habitats that are:

Answer 26

permanent -- rainforests, open ocean, large lakes. resource limited -- crowded, etc.. the organisms tend to be strong competitors.

Question 27

life history strategies summary

Answer 27

evolved in natural selection, differences in: environment, population density, availability of mates (sex ratio) -- always involve trade offs : few vs many offspring parental care vs no parental care reproduce early vs late, many times vs only once.

Question 28

demography

Answer 28

study of populations focusing on birth rates, death rates, age structures, and population growth

Question 29

r strategy relative to demography

Answer 29

produce many offspring therefore they have a high birth rate. their death rate varies with age, most young die, so they have a low survival, but the adults often live long, they have a high survival

Question 30

k strategy relative to demography

Answer 30

maximize fitness, the young have a high sruvival because of the parental care, but the adults have lower survival due to old age, and post reproductive years.

Question 31

draw a survivorship cure for r and k strategy of cod and whales, label and interpret

Answer 31

whale on top (k) and cod on bottom (r), r represents that all are alive at age 0, but they all rapidly die off, k represents that all alive at 0, and overtime, adults die off due to old age.

Question 32

what do we use to construct a survivorship curve

Answer 32

the cohort method -- tracking group of individuals over time

Question 33

types of survivorship curves

Answer 33

type 1, type 2, and type 3. type 1 -- k-strategist, produce few offspring, most survive type 2 -- steady/constant decline type 3 -- r-strategist, produce many offspring, most die.

Question 34

age pyramid

Answer 34

divided by sex, age is increasing by 5 year incriments. measures the population of each age groups

Question 35

death rate stats in canada -- males

Answer 35

they are slightly higher than females, could be due to biological interruptions, cultural factors, risk taking..

Question 36

what are the two things that contribute to populatiion structure

Answer 36

birth rate and death rate

Question 37

spindle shape

Answer 37

draw. Canada and china. boomer bulge, echo generation in their late 20s, large decline in birth rate in recent years.

Question 38

concave shape

Answer 38

Niger, mortality rates are higher, LITTLE decline in birth rate, higher death rate

Question 39

Convex shape

Answer 39

India. Birth rate declining, lower death rate.

Question 40

total fertility rate TFR

Answer 40

number of children per female over lifetime

Question 41

CANADA TFR

Answer 41

canada is growing without high birth rate (immigration exceeds emmigration so positive net migration) -- the TFR is fairly low, therefore without immigtration, canadas population would be decreasing.

Question 42

replacement TFR

Answer 42

2.1 -- we would get a population growth of 0

Question 43

population inertia -- china

Answer 43

population may keep growing even after TFR declines due to AGE STRUCTUREEEE -- CHinas population continued growing after 1 child policy, because cohorts were at reproductive ages, therefore pop was still increasing but slower.

Question 44

global growth rate and population

Answer 44

right now at around 1% growth rate, we will most likely get to 10 billion later on in century

Question 45

word population growth summary

Answer 45

-- the worlds 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 (those wo are entering reproductive stages) keep growing for a time after they reach replacement TFR. (before population stabilizes)