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Understand the Distribution of Organisms

Worksheet Overview

QUESTION 1 of 10

An ecosystem is made up of all the organisms that live in it and their surroundings - for example, your garden is an ecosystem. The living organisms, plants, animals and microorganisms make up the community of the ecosystem.

A habitat is where an organism lives - ants in the garden live in the soil, so the soil is their habitat. Biodiversity describes the range of organisms that live in an ecosystem. All members of the community depend on each other and on the physical factors of their ecosystem,  for example: temperature, humidity, rain, air quality and light availability. A plant that lives in the shade of a big tree does not need that much light for photosynthesis, but other plants only grow well in places with plenty of sunlight.


There are natural ecosystems - like the ocean, woodlands and lakes - and artificial ecosystems - like an aquarium or an artificial pond. Some ecosystems have not been fully explored yet. Oceans are vast and very deep in certain places -  there are creatures living in them that we may never discover. Fields, on the other hand, are artificial ecosystems and farmers have to control what plants grow there and what animals live in them or nearby, to ensure healthy crops. They use herbicides to remove unwanted plants (weeds), pesticides to control insects and other animals that destroy their crops, and fertilisers to increase crop yield.


Environmental scientists have to estimate the population of species that live in ecosystems. This is done when a species is in danger of extinction or for research purposes. In places like nature reserves, the organisms that live in them have to be monitored to ensure their well-being.


Insects can be collected using pooters or nets:

 

image of how to use a pooter

 

Image of a net

 

Small mammals and insects can be caught with pitfall traps:

 

Image of a pitfall trap

 

The animals caught like this are marked (without harming them) and the different species are noted. They are marked so they are not counted again, and sometimes their dimensions are measured to monitor their growth.

 

Quadrats are used to measure the number of plants in an area:

 

Image of a quadrat

 

They are square frames which are thrown on the ground and the plants inside the frame are counted. Then, the number of quadrats that fits into the relevant area has to be calculated (or estimated if the area is very large) and this number is multiplied by the number of organisms.


Counting all animals of one species in a habitat is very difficult as they move around - birds fly away and some animals may even go underground. The population is often an estimate. The formula used to work it out is:

 

Calculation  for working out population.

 

Now on to some questions!

What is the name given to a number of organisms living together in a particular environment?

What is the name given to this collection of living organisms?

Habitat

Community

Group

What is biodiversity?

The number of organisms within a species that lives in an ecosystem

The range of organisms that live in an ecosystem

The place where organisms live

Select the artificial ecosystems from the list below.

The ocean

A man-made pond

A forest

A river

An aquarium

What do farmers use to remove weeds?

Germicides

Pesticides

Herbicides

What piece of equipment is used to estimate plant populations?

Pooter

Net

Quadrat

Pitfall trap

How does a pooter work?

Insects are sucked in from a tube

You take the insect and place it in the jar

Air is sucked out from one tube and insects are sucked into the other tube

Is the following statement true or false?

 

Populations can easily be counted accurately.

True

False

Following on from Question 8, why is it difficult to count a population?

Animals are stable

Animals do not move around

Animals move around

Estimate a population of wild hare if 50 animals were caught the first time, 45 the second time and 25 of them were marked.

 

Just write the number.

  • Question 1

What is the name given to a number of organisms living together in a particular environment?

CORRECT ANSWER
ecosystem
EDDIE SAYS
Hopefully, you didn't find this too tricky a question to start with. Living organisms that live in a certain place, plus its surroundings make up an ecosystem. It is the combination of all of the organisms - that is plants, animals, fungi, bacteria - all of them!
  • Question 2

What is the name given to this collection of living organisms?

CORRECT ANSWER
Community
EDDIE SAYS
Now this might well have confused you - but you won't be the only one to be a bit muddled. Did you choose habitat instead? There are quite a few different words for this topic and it is very important that you know the exact meaning of each one. If you're not sure about them all, it's a good idea to go back and reread the Introduction to make sure you understand the definitions. The living organisms of an ecosystem make up the community. A community of animals all live in the same environment and therefore affect each other and compete for resources.
  • Question 3

What is biodiversity?

CORRECT ANSWER
The range of organisms that live in an ecosystem
EDDIE SAYS
These options looked very similar, didn't they? Very careful reading was necessary here! The key difference in the wording between the first two options was 'number' and 'range'. Biodiversity is the range of different organisms that live in an ecosystem. High biodiversity is important for the health of an ecosystem - if it gets too low, then it could lead to the collapse of whole species of animals.
  • Question 4

Select the artificial ecosystems from the list below.

CORRECT ANSWER
A man-made pond
An aquarium
EDDIE SAYS
A man-made pond and an aquarium are artificial ecosystems, as they have been created by humans. The ocean, forests and rivers are natural ecosystems as they occur and develop naturally without any intervention from humans.
  • Question 5

What do farmers use to remove weeds?

CORRECT ANSWER
Herbicides
EDDIE SAYS
Herbicides are toxic to plants and are used by farmers to remove weeds and other unwanted plants from their fields. You can remember this because the word 'herb' is a plant you would use when you are cooking - so herbicides kill plants.
  • Question 6

What piece of equipment is used to estimate plant populations?

CORRECT ANSWER
Quadrat
EDDIE SAYS
Quadrats are used to estimate plant populations. The other equipment is used to measure animal and insect populations. Imagine going out and counting every blade of grass in the field - much easier to count them in one metre squared as you do when you use a quadrat.
  • Question 7

How does a pooter work?

CORRECT ANSWER
Air is sucked out from one tube and insects are sucked into the other tube
EDDIE SAYS
Have you ever used a pooter? As air is sucked out of one tube, insects are sucked into the pooter through the other tube. This means that there is no risk of humans accidentally sucking up the insect. To make doubly sure, the tube used for sucking is covered in a piece of gauze. Thank goodness for that!
  • Question 8

Is the following statement true or false?

 

Populations can easily be counted accurately.

CORRECT ANSWER
False
EDDIE SAYS
Did you opt for the right one here? It is almost impossible to count a population accurately, as there may be far too many organisms to count and others may move around and away from the area. This is why populations are nearly always an estimate.
  • Question 9

Following on from Question 8, why is it difficult to count a population?

CORRECT ANSWER
Animals move around
EDDIE SAYS
This was really asking you to use your common sense - not all science questions require great knowledge! It is almost impossible to count populations of animals accurately because animals move around and may be grouped in such large numbers that it would take forever to count them all.
  • Question 10

Estimate a population of wild hare if 50 animals were caught the first time, 45 the second time and 25 of them were marked.

 

Just write the number.

CORRECT ANSWER
90
EDDIE SAYS
How did you get on with this one? You need to use the formula given in the Introduction: Population = number of animals caught the first time x the number of animals caught the second time ÷ the number of marked animals caught the second time. So, the population = (50 x 45) ÷ 25 = 90 Well done - you've reached the end of this activity. Are you feeling more confident with this topic now?
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