B4

Question 1

What is the role of the carbon and water cycles in ecosystems?

Answer 1

They maintain habitats, fresh water, and nutrient flow; they ensure the cycling of materials.

Question 2

How is carbon removed from the atmosphere in the carbon cycle?

Answer 2

By photosynthesis in green plants and algae.

Question 3

What do plants and algae use carbon for after photosynthesis?

Answer 3

To make carbohydrates, proteins, and fats.

Question 4

How does carbon move up the food chain?

Answer 4

By animals eating plants and algae.

Question 5

How is carbon returned to the air by living organisms?

Answer 5

Through respiration of plants, algae, and animals.

Question 6

How do decomposers return carbon to the air?

Answer 6

They respire while breaking down dead organisms and waste.

Question 7

What do decomposers return to the soil?

Answer 7

Mineral ions.

Question 8

What process returns carbon to the air from fossil fuels and wood?

Answer 8

Combustion.

Question 9

How is water vapour formed in the water cycle? (2 ways)

Answer 9

Evaporation from seas and lakes.
Transpiration in plants.

Question 10

What causes water vapour to rise and form clouds?

Answer 10

Condensation

Question 11

How is water returned to the land in the water cycle?

Answer 11

Precipitation (rain, snow, or hail).

Question 12

Where does precipitation run into, and why is it important?

Answer 12

Lakes, providing water for plants and animals.

Question 13

Where does the water go after lakes?

Answer 13

Into seas, restarting the cycle.

Question 14

What is decomposition?

Answer 14

Breakdown of dead matter, fallen leaves, or animal droppings by decomposers (bacteria or fungi).

Question 15

What do decomposers secrete?

Answer 15

Enzymes to break material into smaller soluble food molecules.

Question 16

What are the 3 factors that affect decomposition rate?

Answer 16

Temperature
Water availability
Oxygen availability

Question 17

How does temperature affect decomposition?

Answer 17

Warmer = faster reactions, but too hot = enzymes denature, stops decomposition.

Question 18

Why does water affect decomposition?

Answer 18

Needed for respiration and makes food easier to digest.

Question 19

Why is oxygen important for decomposition?

Answer 19

Most decomposers respire aerobically.

Question 20

What is compost?

Answer 20

A product of decayed biological material, used as natural fertiliser by farmers.

Question 21

How is compost made faster?

Answer 21

By providing oxygen (aerobic respiration produces heat) and raising temperature.
Increase in temp means increased rate of decay so compost made quicker

Question 22

What is the first organism in a food chain?

Answer 22

A producer (e.g., green plant or algae).

Question 23

What do producers make and how?

Answer 23

Glucose via photosynthesis.

Question 24

What is the first consumer in a food chain called?

Answer 24

Primary consumer.

Question 25

What are secondary and tertiary consumers?

Answer 25

Secondary = eat primary. Tertiary = eat secondary; food chains usually don’t go beyond this.

Question 26

What does a stable community show?

Answer 26

Population cycles between predators and prey.

Question 27

What happens when prey population increases?

Answer 27

Predator population increases too

Question 28

What happens after predators increase due to increase in prey?

Answer 28

Prey population decreases due to more consumption by predators

Question 29

What happens when prey becomes scarce?

Answer 29

Predator population decreases → prey population rises again.

Question 30

What is a species?

Answer 30

A group of similar organisms that can breed and produce fertile offspring.

Question 31

What is a habitat?

Answer 31

The place where an organism lives.

Question 32

What is a population?

Answer 32

All the organisms of one species in a habitat.

Question 33

What is a community?

Answer 33

Different populations living and interacting in the same habitat.

Question 34

What is an ecosystem?

Answer 34

A community and its interaction with non-living (abiotic) parts of the environment

Question 35

What is an abiotic factor?

Answer 35

A non-living factor that affects organisms.

Question 36

What is a biotic factor?

Answer 36

A living factor that affects organisms.

Question 37

Name 4 abiotic factors that affect communities.

Answer 37

Light intensity Temperature Moisture levels Soil pH and mineral content

Question 38

How does light intensity affect communities?

Answer 38

Required for photosynthesis → affects rate of plant growth → affects food/shelter for other organisms

Question 39

How does temperature affect communities?

Answer 39

Influences rate of photosynthesis.

Question 40

How does moisture level affect communities?

Answer 40

Both plants and animals need water to survive.

Question 41

How does soil pH and mineral content affect communities?

Answer 41

Affects rate of decay (how fast mineral ions return to soil) and nutrient availability for plants.

Question 42

Why do different plants grow in different soils?

Answer 42

Because of varying nutrient concentrations.

Question 43

Name 4 biotic factors that affect communities.

Answer 43

Food availability New predators New pathogens Competition

Question 44

How does food availability affect population size?

Answer 44

More food = more breeding success → population increase.

Question 45

Why are new predators a threat?

Answer 45

They reduce population sizes by consuming prey.

Question 46

Why are new pathogens a threat?

Answer 46

Population has no resistance = population can be wiped out quickly.

Question 47

How does competition affect populations?

Answer 47

Better-adapted species outcompete others, leading to decline in lesser-adapted species.

Question 48

What is competition in biology?

Answer 48

Organisms compete for resources they need to survive.

Question 49

What might plants compete for?

Answer 49

Light, space, water, mineral ions.

Question 50

What might animals compete for?

Answer 50

Space, food, water, mates.

Question 51

What is interdependence?

Answer 51

How organisms depend on others for vital services (food, shelter, pollination, seed dispersal).

Question 52

How can adding/removing species affect a community?

Answer 52

Changes prey or predator numbers → affects population balance.

Question 53

What is a stable community?

Answer 53

All abiotic and biotic factors are balanced; population sizes remain fairly constant.

Question 54

Why are stable communities difficult to replace?

Answer 54

When lost, their balance of conditions and organisms is hard to restore.

Question 55

Give examples of stable communities.

Answer 55

Tropical rainforests, oak woodlands, coral reefs.

Question 56

What are trophic levels?

Answer 56

The stages in a food chain.

Question 57

What is Level 1 in a food chain and what does it include?

Answer 57

Producers – e.g., plants and algae that make food by photosynthesis.

Question 58

What is a primary consumer?

Answer 58

An organism that eats producers – usually herbivores.

Question 59

What is a secondary consumer?

Answer 59

An organism that eats primary consumers – usually carnivores.

Question 60

What is a tertiary consumer?

Answer 60

An organism that eats other carnivores – top predators.

Question 61

What are apex predators?

Answer 61

Tertiary consumers that have no predators.

Question 62

What do pyramids of biomass show?

Answer 62

The relative biomass at each trophic level.

Question 63

What does each level of a pyramid of biomass represent?

Answer 63

The relative weight of material at each level.

Question 64

What happens to biomass as you move up trophic levels?

Answer 64

It decreases.

Question 65

Why is biomass higher at the bottom of the pyramid?

Answer 65

Because not all food is converted to biomass in consumers.

Question 66

How much energy from sunlight do producers transfer to biomass?

Answer 66

About 1%.

Question 67

Why is only 10% of biomass passed on to the next level?

Answer 67

Most biomass is lost due to respiration, waste products, or being inedible

Question 68

Give 3 reasons why not all biomass is transferred.

Answer 68

Not all biomass can be eaten (e.g. bones). Some is lost as waste (e.g. faeces, urea). Some is used in respiration to release energy.

Question 69

Why can biomass be lost as faeces?

Answer 69

Herbivores don’t digest all material they eat.

Question 70

What is the formula for efficiency of biomass transfer?

Answer 70

(Biomass transferred to the next level ÷ Biomass available at the previous level) × 100

Question 71

Why are there fewer organisms in higher trophic levels?

Answer 71

Because less biomass is transferred each time.

Question 72

What is egestion?

Answer 72

waste products that cannot be digested (eg teeth of prey) removed by faeces

Question 73

What is excretion?

Answer 73

Waste products produced by the body removed through excretion eg urea thru urine