Populations In Ecosystems

Question 1

Ecosystem definition

Answer 1

All the organisms living in a community plus all the non living conditions in the area in which they live

Question 2

Community definition

Answer 2

A group of interacting populations of different species living in the same place at the same time

Question 3

Population definition

Answer 3

A group of organisms belonging to the same species found in the same area at the same time and potentially able to interbreed

Question 4

Habitat definition

Answer 4

The environment in which an organism or population of organisms usually lives

Question 5

Biotic definition

Answer 5

The living features of an ecosystem, for example, the presence of predators or food

Question 6

Abiotic definition

Answer 6

The non living features of an ecosystem , such as the temperature and the soil

Question 7

Niche definition

Answer 7

The role of a species within its habitat, for example what it eats, when and where it feeds

Question 8

A niche can

Answer 8

Only be occupied by one species

Question 9

The niche a species occupies includes

Answer 9

Biotic interactions- living interactions, what the organism eats and and what it’s eaten by

Abiotic interactions- non-living interaction, the temperature range an organism can live in or the time of day an organism is active

Question 10

Competitive exclusion

Answer 10

If 2 species try to occupy the same niche, one will be more successful and out compete the other

Question 11

Population size is

Answer 11

The total number of organisms of one species in a habitats

Question 12

Carrying capacity is

Answer 12

The maximum population size that can remain sustainable in an ecosystem

Question 13

Abiotic effect on population size

Answer 13

When abiotic factors are ideal a population will grow and they can reproduce quicker

I conditions are less favorable, the organism will grow much slower and population may decrease

Question 14

3 types of biotic effects that influence population size

Answer 14

Inter specific competition

Intra specific competition

Predation

Question 15

Inter specific competition

Answer 15

Competition that occurs between different species
Competing for the same resources such as food or habitats
Less energy available for growth
One species will out compete and its population will grow
This is known as competitive exclusion principle
This is why two species can’t occupy the same niche

Question 16

Intra specific competition

Answer 16

Competition between members of the same species
Varies around the carrying capacity
Increases or decreases depending on resources available

Question 17

Predation

Answer 17

Population sizes of predator and prey are inter linked
Selection pressure , members of the species who are better adapted to escape or hide from predators can survive
This ensures each new population is better adapted to survival
There are often other factors influencing such as food available for prey

Question 18

Investigating population growth of bacteria

Answer 18

Growing bacteria in a liquid broth
When light is passed through, some is scattered where the bacteria is
Spectrophotometer measures the light passing through and produce an absorbance value
The more bacteria means more absorbance
Graph of absorbance against time is exponential
We use log 10 scale so it is a straight line

Question 19

Abundance definition

Answer 19

The number of individuals of one species in a particular area

Question 20

2 ways abundance can be measured

Answer 20

Frequency- the number of samples a species is recorded in

Percentage cover- how much of the area you are investigating is covered by species, can only be used for non mobile or slow moving species

Question 21

Distribution definition

Answer 21

How a species is spread across a habitat
A species could be evenly spread throughout the whole habitat, they could favour a specific area within an ecosystem or they could be randomly spread

Question 22

Why use random sampling

Answer 22

If an area is too large, or finding the population size would be too time consuming
Take random samples of an area to give a representation of the population size
Must be taken at random to remove any bias
Larger sample size means more representative

Question 23

Process of random sampling

Answer 23

1. Choose an area to sample
2. Devise a method whic will allow for random samples to be taken at a random location, such as a random number generator
3. Use an appropriate sampling technique
4. Take as many samples as possible(minimum 20)
5. Carry out statistical analysis on the data

Question 24

Frame quadrat

Answer 24

Large square divided into smaller squares

Used to sample organisms on the ground in an area that is relatively uniform

Question 25

Quadrat can be used to find

Answer 25

Species frequency- likelihood of a particular species occurring within the quadrat, eg if it’s found in 15/30 squares the frequency is 50%
Number of individuals- number of each species in each quadrat
Percentage cover- number of squares covered by a species (square has to be more than half covered)

Question 26

Transects

Answer 26

Lines through the study area along which samples are taken
Used to help find how organisms are distributed across an area
Useful if there is a change in factor acrosnan area

Question 27

Two types of transect

Answer 27

Belt transects- quadrat a are placed next to each other along the line of study, this can be used to calculate the species frequency and percentage cover

Interrupted belt transects- place quadrats at regular intervals along the line of study

Question 28

Mark release recapture

Answer 28

Capturing an individual of species and harmlessly marking them
Marked animals are then released back to the environment
A second sample can then be captured and count the number of individuals that are already marked

Question 29

Total population size equation

Mark release recapture

Answer 29

Total population size=

No. In first sample x no. In second sample / no. Marked in second sample

Question 30

Accuracy of mark release recapture (4)

Ethical issues (2)

Answer 30

Relies on assumptions:

1. Marked sample has had enough time to mix with unmarked population
2. Marking hasn’t affected chance of survival
3. Mark is still visible
4. There are no changes in population size such as births or deaths

Ethical issues:

1. Organisms could be stressed after capture which could lead to reduced chance of survival
2. Some organisms may be more likely to enter a trap if they’ve already been caught