Populations

Question 1

Population size =

Answer 1

No. individuals in selected quadrats /no. selected quadrats
X total no. quadrats

Question 2

Population density

Answer 2

Population size/ area
X total no. quadrats
= no of individuals per m ^2

The number of that species per unit area

Question 3

Proportion of marked organisms in the population is equal to the proportion of marked organisms in the sample

Answer 3

M/N = m/n

Question 4

Population size estimated

Answer 4

N = Mn/m

Question 5

N is

Answer 5

The population size to be estimated

Question 6

M is

Answer 6

The number of members of the population that are captured initially and marked

Question 7

n is

Answer 7

The number of members of the population that are present in the second capture

Question 8

m is

Answer 8

The number of members of this second capture that are marked

Question 9

Quadrats

Answer 9

Square or circular frame to mark out an area to be sampled

Question 10

Transects

Answer 10

Is a line marked through an area of study (a rope or a piece of string)
Chose a line that has the most plants/immobile animal groups
Use them when the studied area is too big for quadrats
May not give an accurate representation of the diversity and populations of species

Question 11

Capture-recapture

Answer 11

Technique for estimating a population size of mobile species
Relies on the captured sample redistributing equally throughout the population and being recaptured at the same frequency as individuals that have not been captured

Question 12

Carrying capacity

Answer 12

The maximum population size of the species that the environment can sustain
Determined by the amount of available resources (food, water, habitat)

Question 13

Density dependence

Answer 13

As the density of individuals in a population increases, these individuals within the same species begin competing with each others or with other species for the available resources.
In which per capita population progressively fewer resources will be available to sustain it

Question 14

Population dynamics

Answer 14

Refers to the ecological (biotic and abiotic) interactions that lead to fluctuations in population size. It includes how populations of a species change in size and structure over time

Question 15

The abundance

Answer 15

Of a species is a specific measure of a populations size or density in an ecosystem. It’s not just a measure of the number of individuals; it includes specifically where in the habitat they live, breed or hunt

Question 16

r - selected

Answer 16

• Pattern of rapid increase, were the maximum reproductive potential of the species is reached, then the population declines (or crashes) in numbers
• To survive they must colonise new environments quickly
• The species in this group are characterised by being of smaller size, having short life cycles and, in animals, a lack of parental care for young
• They grow and reproduce quickly

Question 17

r - selected examples

Answer 17

Mice
Toads
Weeds
Oysters
Locusts

Question 18

K - selected

Answer 18

Live longer, longer breeding cycles, bred later in life, have fewer offspring and devote time and effort to ensuring the survival of the offspring to reproductive maturity
They are typically strong competitors in a crowded niches that invest more heavily in fewer offspring, each of high has a relatively high probability of surviving to adulthood

Question 19

K - selected examples

Answer 19

The female red kangaroo is able to manage the number of young that are born at any time
Humans
Elephants
Gorillas

Question 20

Population composition

Answer 20

The characteristics of a population, such as age, sex ratios, age structure, population infertility rate and average number of offspring per female

Question 21

Population growth rate (r)

Answer 21

(Birth rate + immigration rate) - (death rate + emigration rate)
(b+i) - (d+e)

Question 22

Measuring distribution (3 types)

Answer 22

random distribution - irregularly spaced
Uniform (continuous) distribution - evenly spaced
Clumped (grouped) distribution - grouped together

Question 23

Population growth curves

Answer 23

When a few members of a species colonise new and favourable habitat, their population increases rapidly

Question 24

Density-dependent factors

Answer 24

Are biotic and include, predation, interspecific and intraspecific competiton, and the spread of disease
These only come into play when the population reaches a certain level, the larger the population, the stronger the impact

Question 25

Density-independent factors

Answer 25

Affects all individuals in a population, severe weather conditions, volcanic activity or habitat destruction by clearing or fire
The chance of individuals surviving the impact of density-independent factors is the same independent of the population entity or size

Question 26

Ecological niches

Answer 26

The way in which species function within their environment - the time they feed, what they feed on, where they live and when they reproduce
The concept of a niche includes the food sources and feeding activities of a species, its spatial habitat, its reproductive site and activities, its relationships and interactions with other species, and any abiotic factors that help the species perisit

Question 27

Fundamental niche

Answer 27

Is the ideal niche a species would occupy if there were no competitors, predators or parasites

Question 28

The realised niche (actually niche)

Answer 28

Is narrower
It results from an organism’s inability to exploit the resources of its habitat because of restrictions asked by other organisms
It is the actual space occupied by a species/organism

Question 29

Resource partitioning

Answer 29

The division in the use of sources is called resource partitioning
Different species within an ecosystem generally don’t feed on the same food sources at the same time. They usually differ in the food source they prefer, their use of space and even the timing of activities

Question 30

Competitive exclusion principle

Answer 30

The competition exclusion principle postulated that no two species can occur the same niche in the same environment for an extended period of time. Two similar species that compete for a resource cannot coexist in the same community

Question 31

A keynote species

Answer 31

Is not necessarily abundant in number in a food web
The niche of a keystone species includes highly influential relationships with a number of other species in a food web.
A keystone species can have a large effect on population numbers of other species in a community even though it may not be abundant. It can prevent organisms from lower tropic levels form monopolising food resources and space