Obj 2- Section A

Question 1

Ecology

Answer 1

the study of the interrelationships of living organisms with each other and with their environment.

Question 2

Environment

Answer 2

the combination of factors that surround and act upon an organism

Question 3

Biotic factors:

Answer 3

all the other living organisms that are present such as predators, prey, competitors, parasites and pathogens

Question 4

Abiotic factors

Answer 4

Abiotic factors: all the non-living chemical and physical factors

Question 5

Habitat:

Answer 5

the place where a particular organism lives.
For example, the habitat of an earthworm is the upper layers of the soil.

Question 6

Species

Answer 6

a group of organisms of common ancestry that closely resemble each other and are normally capable of interbreeding to produce fertile offspring

Question 7

Population:

Answer 7

all the members of a particular species living together in a particular habitat. For example, all the sea urchins living in a sea grass bed form a population.

Question 8

Community

Answer 8

all the populations of different species living together in a particular habitat. For example, a woodland community consists of all the plants, animals and decomposers that inhabit the wood.

Question 9

Ecosystem

Answer 9

a community of living organisms interacting with each other and with their abiotic environment

Question 10

Niche

Answer 10

the position or role of an organism within an ecosystem. For example, an earthworm’s niche is to burrow through the soil, improving its aeration, drainage and fertility.

Question 11

Why carry out an ecological study?

Answer 11

• identify diff species present
• where they live
• determine their numbers
• study relationships that they have with each other and with the abiotic factors

Question 12

Why collect organisms?

Answer 12

-identify organisms

Question 13

in which way can organisms be collected?

Answer 13

Pooters, pitfall traps, nets, plankton nets and a Tullgren funnel may be used

Question 14

List the 4 sampling techniques

Answer 14

• Observations
• Quadrats
• Line transects
• Belt transects

Question 15

Observation

Answer 15

The ecosystem should first be observed and the common species of plants and animals recorded. Any adaptations that enable the organisms to survive in the ecosystem should be noted, together
with any interrelationships between the organisms

Question 16

Quadrat

Answer 16

• square frame with a known area
• placed at random several times
• num. of individuals of each species found within is counted.
• the quadrat can be made into a grid using string and the percentage of the quadrat area covered can be estimated.

Question 17

Why do people use quadrats

Answer 17

Used to study the distribution and abundance of plants and stationary or slow moving animals in uniform ecosystems

Question 18

Why do people use line transects

Answer 18

Line transects are useful where there is a transition of organisms across the ecosystem, e.g. down a rocky seashore. They give a quick idea of the species present and how they change across the ecosystem

Question 19

How is a belt transect used?

Answer 19

made by placing two parallel line transects across an ecosystem. The species found between the lines are recorded. Alternatively, a quadrat
can be placed alongside one line transect and the number of individuals of each species found within its boundaries is counted. The quadrat is then moved along the line and counting is repeated at regular intervals.

Question 20

How to find species density ( average number of individuals of a given species per m2)

Answer 20

tot. no. of species ÷ (area of quadrat x amount of quadrats used )

Question 21

How to find the total population (total number of individuals of a given species in the area under study)

Answer 21

species density x tot. area of ecosystem studied

Question 22

How to find the species cover ( percentage of ground covered by a given species)

Answer 22

(if quadrat is 1m2)
total percentage of ground that the species covered ÷ # of quadrats used

Question 23

Species frequency

Answer 23

This is the percentage of quadrats in which the given species was found.

Question 24

how does the recapture method work?

Answer 24

It is used to estimate the population size of moving animals (eg. sharks, sea turtles etc.) by collecting a sample of animals of the species and counting them, they are then marked (tag or paint) and released back into the same area and given time to mix with the original population.
A second sample is then collected, counted and the # of marked organisms counted

Question 25

Formula for recapture method

Answer 25

marked organisms recaptured

organisms in 1st sample x # organisms in 2nd sample / # marked organisms recaptured

Question 26

Why are abiotic factors important?

Answer 26

To determine the types and numbers of organisms that exist in a given environment, i.e they influence the distribution and behavior of living organisms

Question 27

List the 3 abiotic factors

Answer 27

edaphic factors
climatic factors
aquatic factors

Question 28

What are edaphic factors?

Answer 28

Those factors that are connected with soil

Question 29

Describe soil

Answer 29

Soil is a mixture of inorganic rock particles, water, air, mineral salts, organic matter and living organisms such as plant roots, small animals and micro-organisms

Question 30

What does soil provide organisms with?

Answer 30

Water, oxygen, nitrogen and mineral nutrients

Question 31

Describe texture of soil

Answer 31

Texture i.e the composition of rock particles are formed from rocks by weathering and are classified by size eg. clay, silt, sand, gravel

Question 32

Size of rock particles of certain types of soil:

Answer 32

Clay- less than 0.002mm
Silt- 0.002- 0.02 mm
Sand- 0.02-2mm
Gravel- greater than 2.0mm

Question 33

What is the impact of soil texture on living organisms?

Answer 33

• Influences the water content of the soil (the smaller the soil particles, the more water held due to capillary and chemical forces ∴ the higher the water content
• Influences the air content of the soil (larger particles -> larger air spaces ∴ higher air content
• Influences the mineral ion content of the soil. (smaller the soil particles, the harder it is to leach) ∴ higher mineral content.
• Influences how easy it is for plant roots to penetrate and animals to burrow through the soil. The larger the particles, the easier to penetrate and burrow through.

Question 34

How is water obtained and what does it do to the soil?

Answer 34

Obtained from rainfall and
held in a thin film around soil
particles by capillarity and
chemical forces.

Question 35

Why is water essential to soil?

Answer 35

• Essential for photosynthesis in plants.
• Dissolves minerals so they can be absorbed by plant roots.
• Prevents the desiccation (drying out) of soil organisms without waterproof body coverings, e.g. earthworms.

Question 36

Where is air present in soil?

Answer 36

Present in the spaces between the soil particles

Question 37

Why is air important in soil?

Answer 37

• Oxygen in the air is essential for aerobic respiration in plant roots and soil organisms.
• Oxygen in the air is necessary for bacteria and fungi to decompose organic matter aerobically to form humus.
• Nitrogen in the air is necessary for nitrogen fixing bacteria to form
  inorganic nitrogenous compounds, e.g. nitrates.

Question 38

How are mineral nutrients in the soil formed?

Answer 38

Formed from decomposing
organic matter and by
dissolving from the
surrounding rock. Present as
ions dissolved in soil water

Question 39

Why are mineral salts important in plants

Answer 39

essential for healthy growth

Question 40

What is the optimum pH for most plants?

Answer 40

6.0 to 7.5

Question 41

Why is pH important in soil?

Answer 41

Mainly affects mineral ion availability for plants. If the soil is too acidic or alkaline, mineral ions become less available.

Question 42

Describe humus and how its formed

Answer 42

Formed by bacteria and fungi
decomposing dead or waste
organic matter. Humus is a
dark brown, sticky material
which coats soil particles,
mainly in the topsoil

Question 43

What is the purpose of humus in soil?

Answer 43

• Improves the air content by binding soil particles together in small clumps called soil crumbs.
• Improves the mineral ion content by adding minerals, and absorbing and retaining minerals.
• Improves the water content by absorbing and retaining

Question 44

List the climatic factors that affect terrestrial organisms

Answer 44

light, temperature, humidity, water
availability, wind and atmospheric gases.

Question 45

List the aquatic factors that affect organisms in aquatic habitats

Answer 45

Aquatic organisms are affected by light, temperature, water availability and pollutants in the same way as terrestrial organisms. They are also affected by other factors.