Populations In Ecosystems

Question 1

Define biosphere

Answer 1

The regions of the earth where life exists

Question 2

Define biotic

Answer 2

The living components of an ecosystem

Question 3

Define abiotic

Answer 3

Non living components of the ecosystem

Question 4

Define ecosystem

Answer 4

A community and its abiotic environment. An Ecosystem supports a certain size of population of a species called carrying capacity

Question 5

Define population

Answer 5

A group of individuals of the same species found in the same area at the same time

Question 6

Define community

Answer 6

All the populations of different species living and interacting in a particular place at the same time

Question 7

Define habitat

Answer 7

The place an organism usually lives/ the address of a species

Question 8

What is a niche

Answer 8

The role of a species in an ecosystem, including what it eats, it’s behaviour, where it lives, what eats it. (two species can’t occupy the same niche otherwise there is competition)

Question 9

Abiotic factors and how they determine the size of the population

Answer 9

1. Temperature: every species has optimum at which best able to survive as metabolic processes controlled by enzymes 2. Light: ultimate source of energy for ecosystems, affects the rate of photosynthesis and producers are food for consumers 3. pH: have optimum as affects enzyme action 4. Water and humidity: where water scarce, populations are small and are only those well adapted, humidity affects transpiration and evaporation. Of any factor is below optimum, fewer are able to survive

Question 10

Define competition/ the factors species compete for

Answer 10

results when two or more individuals share any resource (eg. light, food, space/breeding territories etc) that is insufficient to satisfy all their requirements fully.

Question 11

Define intraspecific competition

Answer 11

occurs when individuals of the same species compete for resources. The availability of that resource determines the size of that population. Those best adapted survive and reproduce and pass on their alleles to their offspring (natural selection)

Question 12

Interspecific competition

Answer 12

occurs when individuals of different species compete for resources (one species will usually have a competitive advantage over the other causing it to increase in size and the other to diminish).

Question 13

What is meant by predation

Answer 13

Predation occurs when one organism (the prey) is consumed by another organisms (the predator). Both the predator and prey are animals.
Prey are adapted to hide from the predator (camouflage)Predators are adapted to catch their prey though faster movement, camouflage, ways of detecting prey.

Question 14

How predator prey relationship affects their relative population sizes

Answer 14

An example: 4 year cycles; predator / stoat peaks after prey / lemming; lemmings increase due to low numbers of stoats / available food; more food for stoats so numbers increase; increased predation reduces number of lemmings; number of stoats decreases due to lack of food / starvation; .

Question 15

Factors to consider when using a quadrat

Answer 15

1.The size of quadrat to use - larger species require larger quadrats. If a species is unevenly distributed, a large number of small quadrats will give more representative data than fewer large quadrats. 2The number of sample quadrats to record - larger sample size will give more reliable results 3.The position of each quadrat within the study area - random sampling avoids bias

Question 16

What is the abundance

Answer 16

The number of individuals in a given space/ area

Question 17

How to calculate the abundance using a quadrat

Answer 17

Only used for counting sessile or slow moving organisms. 1.Place 2 tape measures at right angles to set up a coordinates grid.2.Obtain random numbers using a calculator/random number generator/a table to get coordinates. 3.Place the quadrat at the intersection of each pair of coordinates and count the number of x inside.4. Repeat for at least 10 samples and calculate the mean number per quadrat.5. Multiply the mean number per quadrats by the number of quadrats in the x area / find mean number per quadrat which is per 0.25m squared then x 4 to find per m squared then times by total area

Question 18

How to find the percentage frequency using quadrats

Answer 18

Obtain random numbers and place along right angles tape measures at the coordinates. After positioning the quadrat, just record the presence or absence of the species that you are interested in.
If the species is present in 20 out of 40 quadrats then the percentage frequency is 50 %

Question 19

How to find percentage cover using quadrat

Answer 19

After positioning the quadrat, estimate the area in the quadrat that is covered by the species. /Obtain random numbers using a calculator to get coordinates to place quadrats.
Measure % cover of x for at least 10 samples.
Add up the total percentage and divide by the number of quadrats

Question 20

How a belt transect is used to obtain quantitative data about changes in communities along a line

Answer 20

Lay out a tape measure as a transect line along the area of interest (where gradient exists)
Place a quadrat next to the tape measure at 0 m.
Record abiotic data inside the quadrat (if appropriate).
Count the number of species inside the quadrat.
Move the quadrat further along the line and repeat at regular intervals.

Question 21

Ecology definition

Answer 21

The study of inter relationships between organisms and their environment

Question 22

Define succession

Answer 22

Ecosystems are dynamic systems, ecological succession is the process of change in the species structure of an ecological community over time

Question 23

The difference between primary and secondary succession

Answer 23

Primary occurs when bare rock or barren land is present and is first colonised by a pioneer species. Secondary is land that previously sustained life is altered- it occurs more rapidly as soil already exists and spores/seeds may be alive and disperse

Question 24

Outline the process of succession

Answer 24

1. Begins with colonisation by a pioneer species, these change the abiotic environment, causing it to become less hostile 2. These changes means it’s more suitable for the next species to survive and less suitable for the current species 3. This leads to an increase in biodiversity and a greater number/ variety of habitats and niches, also more complex food chains. 4. There is an increase in biomass and the process continues until a stable climax community is reached

Question 25

The features of a pioneer species

Answer 25

Asexual reproduction (rapidly reproduce to form a population), production of large quantities of wind dispersed seeds or pores (spread easily and reach isolated areas). Ability to photosynthesise as no food, ability to fix nitrogen from atmosphere (as no soil nutrients), tolerance to extreme conditions

Question 26

The features of a climax community

Answer 26

Same numerous species present ver long periods of time (a stable community), abiotic factors more or less the same over a long period of time, population numbers stable over long periods of time (around maximum carrying capacity)

Question 27

How to conserve habitats

Answer 27

Species that exist in the earlier stages of succession are no longer present in the climax community because their habitats have have disappeared as a result of succession (change in the community/abiotic environment) or competition or human activity
One way to conserve these habitats (and their species) is by managing succession (preventing it from changing to the next stage)

Question 28

Reasons for conservation

Answer 28

Personal - to maintain our planet (which is our life support system).
Ethical - other species have occupied the Earth far longer than us and should be allowed to coexist with us. We should respect other living things.
Economic - living organisms have a huge pool of genes with the capability to make millions of substances which may be valuable to us in the future. Ecosystems also provide many other goods and services that benefit humans.
Cultural and aesthetic (appreciation for beauty) - habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires writers, poets, artists, composers and others who entertain and fulfill us

Question 29

Describe the mark, release, recapture method

Answer 29

1. An area is defined and marked off and a selection of x are captured, counted, marked and released. 2. The marking must not be easily removable, not harm or affect the survival chances of x 3. Allow time for x to randomly distribute/ reintegrate 4. Collect and count a second sample and count how many are marked. 5. The population size is sample 1 times sample 2 divided by the number marked in the second sample

Question 30

What assumptions are needed for mark release recapture method

Answer 30

There are no changes in the population size during sampling due to em/immigration, births or deaths. Marking does not affect survival or rub off and the marked individuals have time to mix with the population