23.1 Ecosystems

Question 1

What is an ecosystem?

Answer 1

• All the living organisms which interact with one another in a defined area.
• And the physical factors present in that region.

Question 2

What are biotic factors? Give examples.

Answer 2

• Living factors.
• e.g. competition (intraspecific within species/interspecific between species), predation

Question 3

What are abiotic factors? Give examples.

Answer 3

• Non-living factors
• e.g. temperature, light intensity, CO2 concentration, rainfall, pH, humidity

Question 4

What is a habitat?

Answer 4

An area in which organisms live within an ecosystem.

Question 5

What is a population?

Answer 5

A group of animals or plants of the same species living in the same habitat.

Question 6

What is a community?

Answer 6

All the populations of living organisms in a particular habitat.

Question 7

What is a (ecological) niche?

Answer 7

The role of an organism in its community.

Question 8

What are producers?

Answer 8

Organisms which convert light energy into chemical energy by photosynthesis.

Question 9

What are primary consumers?

Answer 9

Obtain energy by feeding on producers?

Question 10

What are secondary consumers?

Answer 10

Obtain energy by feeding on primary consumers.

Question 11

What are tertiary consumers?

Answer 11

Obtain energy by feeding on secondary consumers.

Question 12

What are decomposers?

Answer 12

Break down dead organisms, releasing nutrients back into the ecosystem.

Question 13

How does pH affect an ecosystem?

Answer 13

• Affects the organisms that can live in water, disrupts balance of ecosystem by damaging organisms or inhibiting growth and reproduction
• Changes in soil pH affect availability of soil nutrients

Question 14

How does humidity affect an ecosystem?

Answer 14

• Promotes growth and reproduction of pathogens causing plants to die
• Low humidity leads to increased rate of transpiration which can cause uncontrolled water loss and wilting

Question 15

How does temperature affect an ecosystem?

Answer 15

• Mostly affects enzymes controlling metabolic reactions
• Plants and ectothermic animals develop more rapidly in warmer climates
• Changes in temp can trigger migration/hibernation of animals
• Can trigger leaf-fall/dormancy/flowering in plants

Question 16

How do pollutants affect an ecosystem?

Answer 16

Certain pollutants can have specific impacts:
- Ozone damages tree leaves
- Excess sulfur leads to excess acid in lakes and streams, and damages trees and forest soils.

Question 17

How does light intensity affect an ecosystem?

Answer 17

• Required for photosynthesis - in general greater light availability leads to greater success of plant species
• Plants adapt to cope with different light intensities, e.g. plants in lower LI may have larger leaves or photosynthetic pigments requiring less light

Question 18

How does water availability affect an ecosystem?

Answer 18

• Lack of water leads to water stress, can lead to death
• In plants may lead to wilting as water is required to keep cells turgid
• Required for photosynthesis of plants
• Leads to domination of xerophytes

Question 19

How does oxygen availability affect ecosystems?

Answer 19

• Affected by flow of water, which carries O2
• Beneficial to have fast-flowing cold water - contains high conc of oxygen.
• If water is too warm/flow rate is too slow, O2 concentration drops and aquatic organisms suffocate
• In waterlogged soil, air spaces between soil particles are filled with water, reducing O2 available for plants

Question 20

How do edaphic (soil) factors affect ecosystems?

Answer 20

Different soil types have different particle sizes, affecting organisms living in them:
- Clay - fine particles, so is easily waterlogged and clumps when wet
- Loam - different sized particles, which retain water but does not become waterlogged
- Sandy - coarse, well-separated particles that allow free draining

Question 21

Why are ecosystems described as dynamic?

Answer 21

They are constantly changing as a result of living organisms present and environmental conditions.