Year 8 Science – Living Systems: Ecology 1
Practise applying biotic and abiotic ideas, reading food webs and energy pyramids, and interpreting population data including introduced species. 20 questions. 25 minutes.
Which of these is a biotic factor in a desert ecosystem?
Choose the word that completes each blank.
A 1 is all the organisms of one species living in an area, while a 2 is all the populations living there together.
Blank 1: habitat · population · community
Blank 2: ecosystem · habitat · community
A koala population falls after bulldozers clear eucalypt woodland to build houses. Which cause does this show?
Circle 2 words in the sentence below.
The number of fish in a lake depends on these factors. Click the two biotic factors.
temperatureheronsoxygenparasitessalinity
A diagram shows a nitrogen atom moving from soil into a plant, then into a rabbit, then back into the soil through a decomposer. What does this show?
Choose the word that completes each blank.
Decomposers break down dead leaves and release 1 into the soil, where plants can take them up again. This means matter is 2.
Blank 1: nutrients · heat · light energy
Blank 2: used up · created · recycled
Circle 1 word in the sentence below.
In this food chain, click the organism at the third trophic level.
wattle→beetle→lizard→hawk
In a hot week a rock pool shrinks and its snail numbers fall. Which is the abiotic factor behind the change?
Choose the word that completes each blank.
In an energy pyramid the widest layer is for the 1 because they hold the 2 energy.
Blank 1: primary consumers · producers · decomposers
Blank 2: most · same amount of · least
How much energy reaches the secondary consumers? About 10% of the energy passes to each next level.
| Level | Energy (kJ) |
|---|---|
| Producers | 50 000 |
| Primary consumers | 5000 |
| Secondary consumers | ? |
Choose the word that completes each blank.
Cane toads were brought to Australia to control beetles. With few natural 1, their population 2 quickly.
Blank 1: predators · decomposers · producers
Blank 2: fell · increased · stayed stable
A disease kills nearly all the mice. Which organism is most likely to be directly affected by the loss of its food?
| Food | Eaten by |
|---|---|
| Grass | Rabbit |
| Grass | Mouse |
| Rabbit | Fox |
| Mouse | Fox |
| Mouse | Owl |
Choose the word that completes each blank.
Australian mammals evolved in 1 from other continents, so many had few defences against foxes and cats, which are 2 predators.
Blank 1: competition · migration · isolation
Blank 2: native · extinct · introduced
A student grows seedlings in three trays under different light levels to see how light affects height. Which factor should be kept the same in all trays?
Circle 1 word in the sentence below.
In the food chain grass → grasshopper → frog → snake, click the organism with the least energy available to it.
grass→grasshopper→frog→snake
How many fewer bandicoots per km² were there in 2010 than in 2000?
| Year | Foxes per km² | Bandicoots per km² |
|---|---|---|
| 2000 | 1 | 40 |
| 2005 | 3 | 22 |
| 2010 | 6 | 9 |
What percentage of energy is transferred from primary to secondary consumers?
| Level | Energy (kJ) |
|---|---|
| Primary consumers | 8000 |
| Secondary consumers | 1200 |
Choose the number that completes each blank.
Producers have 4000 kJ and primary consumers have 400 kJ. This is a transfer of 1%, so 2 kJ was lost.
Blank 1: 10 · 1 · 90
Blank 2: 400 · 3600 · 4400
All the foxes are removed from the web. What is the most likely long-term effect on the grass?
| Food | Eaten by |
|---|---|
| Grass | Rabbit |
| Grass | Mouse |
| Rabbit | Fox |
| Mouse | Fox |
| Mouse | Owl |
Cane toads reached the area in 2001. Which explanation for the trend in quoll numbers is best supported by what is known about cane toads?
| Year | Northern quolls per 100 ha |
|---|---|
| 2000 | 48 |
| 2003 | 30 |
| 2006 | 11 |