Notes : 5.1-5.4 Populations in an ecosystem

Question 1

Define the term ecosystem.

Answer 1

All the organisms living in a particular area (aka the community) interacting with each other and with their physical environment (i.e. both the biotic and abiotic factors).

Question 2

Define the term Species.

Answer 2

This is a group of closely related organisms that are able to breed and produce fertile offspring.

Question 3

Define the term community.

Answer 3

all the populations of different species which interact together in the same habitat.

Question 4

Define the term habitat.

Answer 4

The area in which an organism lives

Question 5

Define the term population.

Answer 5

All the members of a single species which live in the same area

Question 6

Define biotic factors and give examples.

Answer 6

• Living features of an ecosystem
  e.g - Plants, Animals, Fungi, Bacteria, Protists, Food

Question 7

Define abiotic factors and give examples.

Answer 7

• Non-living features of an ecosystem
  e.g - Air, Water, Soil, Climate, Temperature

Question 8

Define the term niche.

Answer 8

The role of a species within its habitat.

Question 9

How does food availability affect population size ?

Answer 9

More food = Higher chance of survival and reproducing = population can increase.

(Biotic)

Question 10

How does Predation affect population size ?

Answer 10

Question 11

How does new pathogens affect population size ?

Answer 11

Species will have little to no resistance to it = They will struggle to survive = Their population will decline as more organisms die.

(Biotic)

Question 12

How does competition affect population size ?

Answer 12

The species that is best adapted to survive will outcompete the other specie and the population of that specie that is outcompeted will decline.

(Biotic)

Question 13

How does light intensity affect organisms ?

Answer 13

Light is needed by plants for photosynthesis

More light = Increased rate of photosynthesis = Increased plant growth rate.

Question 14

How does Temperature affect organisms ?

Answer 14

Affects the rate of photosynthesis in plants.

Question 15

How does Oxygen levels affect organisms ?

Answer 15

Some aquatic animals can only survive in water with high oxygen concentration.

Question 16

How does Wind intensity affect organisms ?

Answer 16

• Affects the transpiration rate in plants.
• Transpiration affects the rate of photosynthesis as it ensures water and mineral ions are transported to the leaves.

Question 17

What is the niche concept

Answer 17

• The concept that states that only one organism can occupy each niche in a given habitat at a given time.
• if this ever happens the two species will be in direct competition with each other for resources, and one of the two species will out-compete the other, causing it to die out in that particular habitat.

Question 18

Define the term abundance

Answer 18

Abundance can be defined as the number of individuals of a particular
species living in a habitat.

Question 19

Define the term distribution

Answer 19

where a species lives

Question 20

The niche filled by a species determines its ??

Answer 20

Abundance and distribution.

Question 21

Define the term succession.

Answer 21

The changes in species inhabiting an area over time.

Question 22

What is Primary succession ?

Answer 22

• when an ecological community develops in the absence of soil (i.e. from bare rock).
• This may happen after a volcanic eruption which results in the formation of new rock or if the sea level lowers and exposes new land.

Question 23

Describe the stages of Primary succession.

Answer 23

1. Colonisation: Initial colonisers like lichens and mosses establish themselves on bare rock or newly formed land.(There is no soil to begin with, therefore there’s nothing to absorb water.) - pioneer species are specially adapted live in dry, hostile conditions.
2. Soil Formation: As pioneer species die and decompose they form a basic soil called humus. This makes the environment less hostile and changes the abiotic conditions. As soil forms and more water becomes available, other complex organisms will be able to survive here.
3. Intermediate Species: With improving soil conditions, grasses, ferns, and small shrubs start to grow, increasing biodiversity and soil depth.
   The organisms which are best adapted to the changing ecosystem will out-compete and replace those which are less adapted.
4. Climax Community: Over time, the ecosystem develops into a stable, community (e.g., forest or tundra) where species interactions reach equilibrium.

Question 24

What is secondary succession ?

Answer 24

• When the succession occurs on land which has been cleared (usually to ground level) but is not new ground e.g. soil is present etc.

Question 25

What is a plagioclimax ?

Answer 25

A community stabilized by human intervention