Topic 4: Ecology

Question 1

Differentiate between abiotic and biotic factors

Answer 1

Abiotic are the non-living chemical and physical factors in an environment such as temperature, pH, humidity, wind, etc. Biotic factors are the living components of an environment which affect an ecosystem such as diseases, predation, competition, etc.

Question 2

Define species

Answer 2

A group of organisms that can potentially interbreed to produce fertile viable offspring.

Question 3

Define population

Answer 3

A group of organisms of the same species that are living in the same area at the same time

Question 4

Define community

Answer 4

A group of populations living together and interacting with each other within a given area

Question 5

Define habitat

Answer 5

The environment in which a species normally lives, or the location of a living organism.

Question 6

Define ecosystem

Answer 6

A community and its abiotic environment

Question 7

Define nutrient

Answer 7

A nutrient is a substance (found in food) used by an organism to survive, grow and reproduce. There are 6 major nutrients: carbohydrates, fats/lipids, proteins, vitamins, minerals, and water.

Question 8

Distinguish between autotroph and heterotroph

Answer 8

Autotrophs synthesise their own organic molecules from simple inorganic substances/make their own food with energy derived from sunlight or oxidation of molecules. Heterotrophs obtain their organic molecules from other organisms.

Question 9

Differentiate between the types of heterotrophs (consumer, detritivore, decomposer), with an example each

Answer 9

Consumer: ingest organic molecules from living or recently killed organisms such as mammals (e.g. wolves, bears, humans, etc.)
Detritivore: ingest organic molecules found in the non-living remnants of organisms (e.g. dung beetles, millipedes)
Decomposer: release digestive enzymes and then absorb the external products of digestion (e.g. saprotrophs)

Question 10

Compare the fate of energy and nutrients within an ecosystem

Answer 10

Energy flows through an ecosystem and is lost – requires resupply from a constant energy source (e.g. sun)
Nutrients are finite and are recycled within a closed ecosystem

Question 11

Outline the role of decomposers in maintaining nutrient supply

Answer 11

Decomposers release enzymes to externally break down organic material
This allows for inorganic compounds to be replenished within the environment (e.g. returned to the soil)

Question 12

Define mesocosm

Answer 12

A mesocosm is an enclosed environment that allows a small part of the natural environment to be viewed under controlled conditions

Question 13

Identify two methods of population sampling

Answer 13

Quadrats and transects

Question 14

What is the formula for expected frequencies?

Answer 14

(Row total x Column total)/Grand total

Question 15

What is the chi-square formula?

Answer 15

The sum of (O-E)^2/E

Question 16

Identify a null hypothesis

Answer 16

There is no significant difference in the distribution of species (species are not associated)

Question 17

Identify an alternative hypothesis

Answer 17

The is a significant difference in the distribution of species (species are associated)

Question 18

If x^2 > 0.05, do we reject or accept null hypothesis

Answer 18

There is an insignificant difference meaning we accept null hypothesis

Question 19

If x^2 < 0.05, do we reject or accept null hypothesis

Answer 19

There is a significant difference meaning we reject null hypothesis

Question 20

Define trophic level

Answer 20

The position an organism occupies within a feeding sequences. Producers always occupy the first trophic level.

Question 21

Differentiate between food chain and food web

Answer 21

A food chain only shows one or a linear feeding sequence while a food web is more complicated showing multiple food chains.

Question 22

Distinguish between herbivores, carnivores, and omnivores

Answer 22

Herbivore: Feeds exclusively on plant matter
Carnivore: Feeds exclusively on animal matter
Omnivore: Feeds on both plant and animal matter

Question 23

List three ways which energy may be lost from one trophic level to the next

Answer 23

As heat, converted into other form of energy, stored chemical energy remains unconsumed

Question 24

Describe the flow of energy in ecosystems

Answer 24

Light energy (from the sun) is the initial energy source for almost all communities. It is converted into chemical energy (organic molecules) by producers / autotrophs via photosynthesis. The organic molecules are converted into a usable energy form (ATP) via cell respiration. Heterotrophs (consumers) ingest these organic compounds in order to undergo cell respiration. Energy transformations are only ~10% efficient, the majority of the energy is lost as heat

Question 25

Identify the 6 processes involved in the carbon cycle

Answer 25

Photosynthesis, respiration, combustion, decomposition, feeding, and calcium carbonate

Question 26

Write the balanced chemical equation for photosynthesis

Answer 26

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 27

Write the balanced chemical equation for cell respiration

Answer 27

C6H12O6 + 6O2 –> 6CO2 + 6H2O + ATP

Question 28

Outline how carbon is stored in aquatic ecosystems

Answer 28

Some carbon dioxide in water stays as dissolved gas, however most reacts to form hydrogen carbonate ions. When the ions come to contact with rocks/sediments, they commonly form calcium carbonate (limestone). In animals, the calcium carbonate can be used to form hard exoskeletons (e.g. corals and shells).

Question 29

Describe the production of methane by methanogens and its oxidation in the atmosphere

Answer 29

Methanogens produce methane from organic matter as a by-product of anaerobic respiration. The methane can either diffuse into the atmosphere or accumulate within the ground. Methane in the atmosphere is oxidised to carbon dioxide and water after ~12 years.

Question 30

Outline the formation of peat/coal

Answer 30

In anaerobic conditions such as waterlogged soils, saprotrophs can only partially decompose organic matter. The remaining carbon-rich material stays within the soil and forms peat. When compressed under sediment, the high pressure and heat force out moisture and turn peat into coal.

Question 31

Outline the formation of oil/natural gas

Answer 31

Oil and natural gas form as a result of the decay of marine organisms on the ocean floor. Sediments are deposited on top of the organic matter, creating anoxic conditions that prevent decomposition. The compacted and heated organic matter forms oil and gas, which accumulates within porous rocks.

Question 32

Identify three human activities that can trigger carbon fluxes within the atmosphere

Answer 32

Combustion of fossil fuels, deforestation, and agricultural practices

Question 33

Identify the most common greenhouse gas within the Earth’s atmosphere

Answer 33

Water vapour

Question 34

List four other greenhouse gases

Answer 34

Carbon dioxide, methane, nitrogen oxides, fluorinated gases (e.g. CFCs)

Question 35

Identify the two main factors that determine the impact of a greenhouse gas

Answer 35

Ability to absorb long-wave radiation and concentration within the atmosphere

Question 36

Explain the relationship between greenhouse gases and the greenhouse effect

Answer 36

The greenhouse effect functions to trap heat within the atmosphere and prevent rapid temperature changes. Incoming radiation (from the sun) is shorter wave radiation (e.g. ultraviolet radiation and visible spectrum). The Earth’s surface absorbs this radiation and re-emits it at a longer wavelength (i.e. infrared radiation / heat). Greenhouse gases absorb and re-radiate the longer wave radiation and hence retain heat in the atmosphere. The higher the concentration of greenhouse gases in the atmosphere, the more heat is retained, hence global warming if there are too much greenhouse gases in the atmosphere.

Question 37

List three climate conditions that are influenced by greenhouse hases

Answer 37

Global temperatures (increasing), weather conditions (more frequent extreme conditions), ocean currents (changes can cause longer El Nino events).