15. Chapter 53: Population Ecology

Question 1

Biological species concept

Answer 1

1. species interbreed, cannot with other groups

2. difficult to apply in field b/c asexual, hybrids, fossils

Question 2

How have most named species been ID?

Answer 2

morphological characters

Question 3

Cryptic species and evolutionary significant units (ESU) may be indistinguishable. What would be useful to distinguish?

Answer 3

Genetics

Question 4

How would a biologist ID populations?

Answer 4

1. Determine (guess) gene flow b/w these pops.

2. separation often arbitrary

Question 5

3 patterns of dispersion

Answer 5

1. random: position of each individual is independent of others (uniform enviro but no pattern of attraction or avoidance - some forest trees)
2. uniform: evenly spaced apart, a result of intraspecific competition
3. clumps: result of habitat differences, reproductive necessity, offspring dispersal (most common)

Question 6

Temporal dispersion

Answer 6

dispersed in time and space as a response to environmental conditions (food, light) or only clump during mating

Question 7

Dispersal movements

Answer 7

immigrate (into) or emigrate (out) of population

Question 8

migration (an example of dispersal movement)

Answer 8

dispersal with subsequent return to place of origin (enviro adaption to pressures)

Question 9

Migratory examples (7)

Answer 9

1. Zooplankton: lower by day and up at night
2. Elk: high altitude in summer, low in winter
3. Some caribou: calve in tundra, winter in taiga
4. gray whales: food-rich arctic in summer, to winter
5. Birds: long-range migrants (Arctic tern)
6. Pacific salmon: one return trip as young and return home to spawn and die
7. Monarch: fall migrants do not return north but offsprings do

Question 10

Four factors of all populations

Answer 10

1. Births
2. Death
3. Immigration
4. Emigration.

Question 11

Population growth equation

Answer 11

N (future) = N (present) + (B-D) + (I-E)

- lots of examples of exponential growth

Question 12

What will halt pop growth?

Answer 12

competition: interaction b/w individuals lead to reduction in survivorship and/or reproduction

Question 13

Define resource

Answer 13

anything that is essential for continuance of life and that is finite

Question 14

Define limiting resource

Answer 14

the resource that is in the shortest supply in relation to organism’s demand for it (nest cavities, sodium) competition is for limited resources

Question 15

Density dependent

Answer 15

effects of competition are likely to be greater as # of competitors increase (i.e mortality vs density graph - line remains straight until density increase then it goes up or down)

Question 16

What is the primary pattern as density increases?

Answer 16

the per capita birth rate eventually decreases and per capita death rises

Question 17

Patterns of density

Answer 17

1. intersection pt where births = deaths = stable pop.
2. if birth > death = pop. increase
3. if death > bith = pop. decrease

Question 18

What is the intersection density known as?

Answer 18

populations carrying capacity (K)

theoretically, all densities tend to approach K but more complex in wild b/c enviro unpredictable therefore K = range

Question 19

Logistic growth

Answer 19

1. growth followed by stabilization (s- shaped, sigmoidal) common as approaches K
2. growth slows as density increases
   (K = flattens out)

Question 20

How is the behaviour of he pop. sensitive to rate of growth?

Answer 20

1. high growth rates = oscillations
2. very high growth rates = chaos
3. accentuated by time lags, climatic variations, predator behaviour

Question 21

How is the ratio of young to adults informative?

Answer 21

1. increase pop. tend to have high young
2. decrease pop. have few young
3. deficiency in young lead to aging pop.

Question 22

Examples of growth rates

Answer 22

1. Kenya: bottom heavy, lots of young, rapid growth
2. US: hourglass: more young than old, slow growth
3. Italy: top heavy, more old than young, no growth, decline

Question 23

What is organismal aging or senescence characterized by?

Answer 23

declining ability to respond to stress, homeostatic imbalance, + risk of disease

Question 24

Ultimate consequence of aging

Answer 24

death (some gerontologist regard age as disease that may be curable)

Question 25

Do we live longer now than in 1800?

Answer 25

No, we just don’t die as young (evolutionary biologist don’t think aging is curable)

Question 26

Define life expectancy

Answer 26

average # of yrs to be lived in future by members of given age in pop.

Question 27

Evolutionary explanation for aging?

Answer 27

grounded in idea that strength of natural selection decreases with age
(i.e. gene for heart attack at 15yrs, strongly selected against but if for 50yrs then weaker selection and genes may have already been past on to next generation)

Question 28

Pleiotropic genes

Answer 28

genes that have more than one effect on phenotype

Question 29

Antagonistically pleiotropic genes

Answer 29

those that have one beneficial effect and one deleterious effect (e.g. testosterone)

Question 30

Why do humans live so long? No other primate has such an extended post-reproductive phase of life.

Answer 30

“grand-parenting theory” - humans teach young, evolutionary advantage to keep older survivors to teach and care for young

Question 31

Let’s say you are studying a population of concern. Often you want to start by gathering basic demographic data. What would that include?

Answer 31

1. pop. size/ density
2. age of members
3. sex ratio
4. birth/death rates
   (experimental error can accumulate at ea. step)

Question 32

How id demographic ideally determined by?

Answer 32

tracking cohort from birth to death. Cohort is members of a pop. that are the same age

Question 33

Define life history

Answer 33

the pattern of growth, reproduction and mortality for individual (or pop.)

Question 34

Define Semelparous

Answer 34

produce offspring in a single reproductive event (i.e. Pacific salmon)

Question 35

Define Iteroperous

Answer 35

produce offspring in series of multiple reproductive events

Question 36

What do life tables allow ecologists to make comparisions between?

Answer 36

sexes, cohorts, populations and species

Question 37

Survivorship curves

Answer 37

shows apparent patterns despite great variety in life histories
(i.e. pattern in relationship b/w mortality and fecunity) Natural selection cannot max. all variable simultaneously - life history trade-offs

Question 38

What are the three hypothetical types of survivorship curves classified as in order to compare to real-life data?

Answer 38

1. Type I curve: high survivorship throughout life then experience heavy mortality in old age (e.g. many mammals)
2. Type II curve is linear: pop. with constant mortality rates (e.g. adult stages of birds)
3. Type III curve is conclave: typical in pop. with high mortality in early life (e.g. fish, invertebrates, some plants)