1-B Ecosystems

Question 1

What is an ecosystem?

Answer 1

A biological community with biotic (living) and abiotic (non-living) components.

Question 2

What do food chains show?

Answer 2

The interrelationships between feeding groups

Question 3

Why does the weight of biomass get smaller at each level?

Answer 3

• Many parts of plants and animals are not eaten. A lot of what is eaten is excreted
• Energy is lost at each level. Hunters use a lot of kinetic energy (chasing prey). Respiration requires lots of energy

Question 4

Describe nutrient cycling

Answer 4

Within an ecosystem, nutrients is constantly being transferred.

For example, decomposers release nutrients from litter into the soil. Plants release nutrients from the soil into biomass. Plants die and nutrients from biomass is transferred to litter.

Question 5

Describe the interrelationships within the ecosystem of Epping Forest, UK

Answer 5

There are large numbers of native tree species (oak, elm, ash and beech)

There is a lower shrub layer of holly and hazel. There is a field layer of grasses and 177 species of moss and lichen. Lots of producers.

There are many insects, mammals and birds. For example, worms, caterpillars, rabbits, mouse, owls, foxes and badgers.

There are 700 species of fungi. There are lots of decomposers.

Question 6

How do we know that the ecosystem of Epping Forest is interdependent?

Answer 6

The deciduous trees lose their leaves for winter. In mid-autumn, the forest floor is covered with a thick layer of leaves.

By spring, the leaf litter has disappeared and the nutrients stored in the leaves are converted to humus in the soil, ready to support the new season’s plant growth

Question 7

How do physical and human forces disturb ecosystem balance?

Answer 7

Physical Forces:
- extreme weather or climate change. (e.g. 1976-77 Summer of England experienced a drought, which killed 15 million trees. This has impacted consumer species greatly)

Human Forces:

• deforestation exposes the soil beneath to rainfall, and so it can be washed away. This makes it impossible for ecosystems to recover.
• human induced climate change can change temperature and precipitation patterns, which make it harder for forests to survive.

Question 8

How does the loss or gain of one species affect a food web?

Answer 8

The introduction or retraction of a specie can impact the consumer above and below the species. Not only this, but the species on its same consumer level will also be impacted.

Question 9

What is an example of a successful restoration of an ecosystem?

Answer 9

Reintroduction of Grey wolves in Yellowstone National Park in the USA:

• elk population fall by 10,000, which leads to reduction in grazing pressure. Less erosion occurs
• coyote numbers fall as competition for food increases. This leads to an increase in voles, mice and other rodents

Question 10

How does climate impact the distribution of global ecosystems?

Answer 10

Climate -

• tropical rainforests found on equator due to high insolation and heavy rainfall.
• deserts found on tropics due to high insolation, but lack of water/rainfall.
• coniferous forests found in areas that have a lack of insolation and in some months, none at all
• tundra is found in the arctic circle where the sun’s rays are weak and temperatures are below freezing for most of the year

Question 11

How does altitude, relief and ocean currents impact the distribution of global ecosystems?

Answer 11

Altitude - temperatures falls by half a degree for every 100-meter increase in altitude. Tough grass replaces trees

Mountain Ranges - inland areas hidden from the sea suffer from low rainfall. Winds blowing off the oceans quickly lose their moisture when air is forced upwards

Ocean Currents - cold ocean currents cause little evaporation to take place. This means that it creates arid conditions and vice versa.