B2.4 - Organisms and their environment

Question 1

What is a habitat?

Answer 1

A habitat is an organism’s living area.

Question 2

What is an organism’s distribution?

Answer 2

The distribution of an organism is where it is found in its habitat.

Question 3

What factors affect a plant’s distribution?

Answer 3

Temperature

Availability of water

Availability of oxygen and carbon dioxide

Availability of nutrients

Amount of light

Question 4

What are abiotic factors?

Answer 4

They are non-living conditions which can influence the distribution of organisms.

Question 5

How do temperatures affect plants (distribution)?

Answer 5

There will usually be more plants in a place with an average temperature as temperature is a limiting factor of photosynthesis.

If there is a high or low temperature, less plants will be found.

Question 6

How does the availability of water affect plants?

Answer 6

Plants will grow near water as they can use water to grow via photosynthesis.

Question 7

How does the availability of oxygen affect plants?

Answer 7

Plants need oxygen to respire and will be found in areas with high quantities of oxygen.

Question 8

How does the availability of carbon dioxide affect plants?

Answer 8

Plants will grow in areas where a lot of carbon dioxide is present as carbon dioxide is a limiting factor of photosynthesis.

It aids growth.

Question 9

How does the availability of nutrients affect plants?

Answer 9

Plants require nutrients, such as nitrate ions, for proteins. These stimulate development, so there will be more plants in an area with more nitrate ions.

Question 10

How does the amount of light affect plants?

Answer 10

Light is a limiting factor of photosynthesis, so plants will be found in areas with more light, like in the middle of a field than under a tree.

Question 11

What is qualitative data? (Distribution)

Answer 11

General words to give us “an idea”

“There are lots of…”

Question 12

What is quantitative data? (Distribution)

Answer 12

Specific, numeric values

“There are 6..”

Question 13

How can we study the distribution of organisms?

Answer 13

We can:

Measure how common an organism is in two sample areas and compare them.

Study how the distribution changes across an area.

Question 14

What is a quadrat?

Answer 14

A quadrat is a square frame that encloses a known area. This could be 1m squared.

Question 15

How is a quadrat used? (The method)

Answer 15

Place the quadrat on the ground (randomly).

Count all of the organisms within the quadrat.

Repeat the first two steps and calculate the mean, median, mode, etc.

Repeat for a second sample area and compare the means.

Question 16

Why is a quadrat thrown randomly? How is this done?

Answer 16

If it’s random then bias is eliminated.

You can throw the quadrat randomly when blindfolded or by throwing it under your shoulder.

A random number generator and a grid may be used so a random point on the grid is selected.

Question 17

What is a limitation of quadrats?

Answer 17

Quadrats only work for slow or immobile populations.

Question 18

Why is it so important to collect lots of data when using quadrats?

Answer 18

It is important to collect lots of data so the results are accurate and reproducible, as well as valid.

Question 19

How do we work out population size?

Answer 19

Work out the mean number of organisms per meter squared.

Multiply the mean by the total area of the habitat.

If an open field is 800m squared and there are 22m squared, then you do 800*22 = 17600

Question 20

What is a transect?

Answer 20

A transect is a line across a habitat or part of a habitat. It may be a string or a tape measure.

Question 21

How is a transect used?

Answer 21

Mark out a line in the area under study by using a tape measure.

Then, collect data along the line by counting or placing quadrats along the line at regular intervals.

Question 22

What is a limitation of transects?

Answer 22

Transects only work for slow or immobile populations.

Question 23

What is reliability?

Answer 23

Reliability is ensuring that results are repeatable and reproducible.

Question 24

How do we ensure reliability?

Answer 24

Take a larger sample size. This is more representative of the whole population.

Question 25

What is validity?

Answer 25

Validity is ensuring that the results are reliable and are capable of answering the original question.

Question 26

Why must all variables be controlled when investigating distribution?

Answer 26

All variables must be controlled so you can determine that the difference in results is an environmental change and not because of a poor experiment.

Random samples must be used to eliminate bias.

Question 27

What is the mean? How do we calculate it?

Answer 27

The average

Add the results up and divide by how many there are.

Question 28

What is the median? How do we work it out?

Answer 28

The middle value

Get the numbers in order and find the middle value.

Question 29

What is the mode?

Answer 29

Most common value