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Distribution of Organisms

In this worksheet, students will study the physical factors of an environment. They examine both the terminology used and how environmental scientists study 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 too 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 at 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 plants:

 

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:

 

Calcification for working out population.

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 two 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

Tick one piece of equipment 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

Considering your answer to Question 8, why is it easy/difficult to count a population?

They 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
Living organisms that live in a certain place and 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
The living organisms of an ecosystem make up the community. A community of animals all live in the same environment and therefore effect each other and compete for resources.
  • Question 3

What is biodiversity?

CORRECT ANSWER
The range of organisms that live in an ecosystem.
EDDIE SAYS
Biodiversity is the range of different organisms that live in an ecosystem. High biodiversity is important to the health of the ecosystems, if it gets too low then it could lead to the collapse of whole species of animals.
  • Question 4

Select the two 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 unwanted plants from their fields. I remember this because the word 'Herb' is a plant you would use when you are cooking - so herbicides kill you cooking pants (if they are not wanted in that farmer's field that is).
  • Question 6

Tick one piece of equipment 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 meter squared like 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
Air is sucked out from one tube and so insects are sucked into the pooter through the other tube. This means that there is no risk of humans accidentally sucking up the insect.
  • Question 8

Is the following statement true or false?

 

Populations can easily be counted accurately.

CORRECT ANSWER
False
EDDIE SAYS
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 an estimate.
  • Question 9

Considering your answer to Question 8, why is it easy/difficult to count a population?

CORRECT ANSWER
Animals move around
EDDIE SAYS
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

Remember to show your calculations, where possible, in exam papers.
---- OR ----

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