lec 15- population structure

Question 1

population

Answer 1

a group of individuals of a single species inhabiting a specific area

Question 2

characteristics of a population

Answer 2

density: number of individuals per unit area
- distribution: size, shape and location of area occupied + how individuals are spread
- other demographic characteristics: age distributions, sex ratios, birth & death rates, immigration & emigration rates, rates of growth

Question 3

distribution

Answer 3

• geographic distribution of a species is limited by the physical environment
• species can only exist in areas where its niche requirements are fulfilled

Question 4

why does population density decline with increasing organism size

Answer 4

1. body scaling
2. metabolic demands vs. resource availability

Question 5

dispersal

Answer 5

• dispersal can alter species distributions and local population densities
• immigration: movement INTO a local population
• emigration: movement OUT OF a local population

Question 6

do same patterns exist in plants?

Answer 6

Same pattern exists in plants but relationship more dynamic in a
plant’s life stages. As a rule of thumb, for a given species, density decreases
with increasing biomass (age) in a process called self-thinning, due to
competition among plants

Question 7

density

Answer 7

• number of individuals per unit area
• absolute density: number of individuals of a population per unit area
• ecological density: number of individuals of a population per unit area suitable habitat

Question 8

do seedlings have high or low density

Answer 8

high, adults have low

Question 9

patterns across the plant kingdom

Answer 9

body scaling and resource
demands vs. availability lead to similar patterns as in animals

Question 10

giant plants (coastal redwood)

Answer 10

have some of the lowest densities.

Question 11

tiny plants like
duckweed

Answer 11

reach some of the highest densities.

Question 12

rarity

Answer 12

How common or rare a species is,
is influenced by:
* Geographic Range of Species
→extreme vs. restricted
* Habitat Tolerance
→broad vs. narrow
* Local Population Size
→large vs. small

Question 13

Rare species with how many aspects of rarity make them prone to extinction

Answer 13

3

Question 14

IUCN

Answer 14

International Union for the Conservation of Nature

Question 15

LC –

Answer 15

– least concern

Question 16

NT – not threatened

Answer 16

not threatened

Question 17

VU

Answer 17

vulnerable

Question 18

EN

Answer 18

endangered

Question 19

CR

Answer 19

critically endangered

Question 20

EW

Answer 20

extinct in the wild

Question 21

EX

Answer 21

extinct (anywhere)

Question 22

Population Structure

Answer 22

Demographic characteristics of populations,
such as survival, age and sex distribution, and
dispersal.

Question 23

population dynamics

Answer 23

Change in population structure and size over time.

Question 24

patterns of survival

Answer 24

• patterns of survival and mortality among individuals in a population is a fundamental descriptor
• life tables: bookkeeping device to track births and deaths in populations, from which to estimate survival
• survivorship curve: summarizes pattern of survival in a poulation

Question 25

how to estimate patterns of survival

Answer 25

• cohort life table
• static life table
• age distribution

Question 26

1. cohort life tables

Answer 26

• identify individuals born at the same time and keep records from birth: comparison by generations
• impossible to track for extremely mobile animals + animals with a long life span
• data easy to interpret

Question 27

2. static life table

Answer 27

• record age at death of large number of individuals over narrow window in time: tables are constructed using one-time observations
• require accurate estimate of age at death

Question 28

3. age distribution

Answer 28

• calculate differences in proportion of individuals in each age class
• assumes differences in numbers from one age class to next is due to mortality
• also assumes population size is stable

Question 29

survivorship curve

Answer 29

graphic summary of the pattern of
survival in a population, based on life table data.

Question 30

type I: high survival of young

Answer 30

• mortality increases in higher age groups
• ex. most large vertebrates, annual plants, rotifers, humans

Question 31

type II: constant rates of survival

Answer 31

• no substantial predation
• not a long life span
• linear relationship
• ex. most birds, robins, sparrows, water snakes

Question 32

type III: low survival of young

Answer 32

• young not expected to survive, so many are laid
• opposite of type I
• ex. fish, trees, other plants

Question 33

age distribution

Answer 33

• reflects its history of survival, reproduction, and growth potential
• by studying the history of a population through describing its age distribution, population ecologists can make predictions about its future

Question 34

why study age distribution?

Answer 34

• understand species stability
• climate problems

Question 35

sex ratios

Answer 35

• population sex ratios can change depending on relative fitness of different sexes
• sex ratio: relative frequency of each sex type in a population
• empirically, most populations have a ratio near 1:1

Question 36

why are sex ratios unequal

Answer 36

The female is always going to have
high fitness, because she is always
going to find a mate.

Only one of the males will be able
to reproduce.

Question 37

Frequency-dependent selection

Answer 37

= Fitness of a genotype depends on its frequency

Question 38

If the ability to produce females is genetic, the relative frequency of female producing individuals is going to increase or decrease in the population?

Answer 38

increase in the population as times goes on, in all subsequent generations.