Population Ecology 2 - Survival and Reproduction

Question 1

Metapopulation

Answer 1

group of populations of the same species that are separated by space but interact to some degree

Question 2

Sink

Answer 2

a population that requires net immigration in order to sustain itself

Question 3

Life History

Answer 3

how energy is allocated into a life cycle (maturity into adulthood, development, and decline into reproductive deterioration) of the organisms survival

• energy allocation generates characteristic LIFE HISTORY TRAITS

Question 4

Life History Traits

Answer 4

traits that impact survival and reproductive output (size at birth, size/age at maturity, # of offspring, fecundity, reproductive value, lifespan and deterioration)

Question 5

Life History Theory

Answer 5

explains how evolution optimizes survival + reproductive characteristics in different populations
- optimized, NOT MAXIMIZED. when evolution increases a trait, the result is usually a decrease in some aspect of reproduction (LIFE-HISTORY TRADE-OFF)

Question 6

Energy Allocation Split

Answer 6

• negative relationship between survival and reproduction
• if one is favored, the other decreases
• energy is finite, so organisms have to have a trade-off between surviving and reproducing

Question 7

Energy Trade-Off w/ Population Ecology

Answer 7

Selection for trade-offs can be related to a population’s growth rate (r) and environment’s carrying capacity (K)

Question 8

r-Selected (Pop. Growth Rate)

Answer 8

life history traits that maximize growth rate (live fast, die young)
- these species exploit ecological niches where they are NOT limited by a carrying capacity
- EX: insects, bacteria, plants, small mammals
- Traits include large # of offspring, small body size, early sexual maturity, short life span, limited parental care
- Pop. size can change dramatically over short periods of time

Question 9

K-Selected (carrying capacity)

Answer 9

life history traits that are selected for in organisms living at densities near environmental carrying capacity
- pop size tends to stay stable and close to max carrying capacity
- EX: large mammals, reptiles, birds
- Traits include small # of offspring, large body size, late sexual maturity, longer life span, higher degree of parental care

Question 10

Reproductive Value

Answer 10

relative number of offspring that remain to be born to individuals of a given age
- influenced by the probability of survival and probability of successful reproduction

Question 11

Reproductive Value Over a Life Span

Answer 11

• at birth, reproductive value tends to increase to a maximum value at or near the onset of sexual maturity
• declines as individuals age
• natural selection acts most efficiently on age classes and life cycle stages with high reproductive value

Question 12

Life Table

Answer 12

analytical tool that population ecologists use to study age-specific population characteristics such as survival, fecundity, and mortality
- determine the # of individuals that survive from one age group to the next

Question 13

Population Demography

Answer 13

study of numbers and rates in a population and how they change over time
- life tables

Question 14

Cohort Tables

Answer 14

follow one group of individuals born at the same time (cohort) until the death of all individuals
- this technique requires 2 key assumptions

Question 15

Cohort Tables: Key Assumptions

Answer 15

1. The population sample of each age class if proportional to its numbers in the population
2. Age-specific mortality rates remain constant during the time period, meaning that subsequent cohorts will exhibit similar patterns of birth and death

Question 16

Survivorship

Answer 16

converts mortality from year to year into a proportion alive of the original cohort (lx=nx/no)

Question 17

Age-Specific Fecundity

Answer 17

the average number of offspring born to individuals of each age (must be estimated from data, not calculated)

Question 18

Net Reproductive Rate

Answer 18

• if the two assumptions are met
• the sum of the product of survivorship and fecundity at each age gives the net reproductive rate
• population growth parameter called Ro

Question 19

Ro > 1

Answer 19

the population is producing more offspring than it is losing in death (population is growing)

Question 20

Ro < 1

Answer 20

the population is producing less offspring than it is losing in death (population is shrinking)

Question 21

Ro = 1

Answer 21

the population is stable

Question 22

Survivorship Curves

Answer 22

graphic representation of the number of individuals in a population that can be expected to survive to any specific age
- patterns of age-specific survival are predictive of the general life history of a population
- lx VS time graph
- Type I, II, III

Question 23

Survivorship Curves: Type I

Answer 23

-observed in populations with low mortality in young age classes but have very high mortality as an individual ages
- Often have low birth rates because most offspring survive to reproduce
- EX: Humans

Question 24

Survivorship Curves: Type II

Answer 24

• populations where the mortality rate is constant regardless of age
• EX: Birds

Question 25

Survivorship Curves: Type III

Answer 25

• occur in populations with high mortality in early age classes and very low mortality in older individuals
• generally need high birth rates for population sizes to remain constant or to have enough offspring survive to reproduce
• EX: Trees