B4 Flashcards
What is the role of the carbon and water cycles in ecosystems?
They maintain habitats, fresh water, and nutrient flow; they ensure the cycling of materials.
How is carbon removed from the atmosphere in the carbon cycle?
By photosynthesis in green plants and algae.
What do plants and algae use carbon for after photosynthesis?
To make carbohydrates, proteins, and fats.
How does carbon move up the food chain?
By animals eating plants and algae.
How is carbon returned to the air by living organisms?
Through respiration of plants, algae, and animals.
How do decomposers return carbon to the air?
They respire while breaking down dead organisms and waste.
What do decomposers return to the soil?
Mineral ions.
What process returns carbon to the air from fossil fuels and wood?
Combustion.
How is water vapour formed in the water cycle? (2 ways)
Evaporation from seas and lakes.
Transpiration in plants.
What causes water vapour to rise and form clouds?
Condensation
How is water returned to the land in the water cycle?
Precipitation (rain, snow, or hail).
Where does precipitation run into, and why is it important?
Lakes, providing water for plants and animals.
Where does the water go after lakes?
Into seas, restarting the cycle.
What is decomposition?
Breakdown of dead matter, fallen leaves, or animal droppings by decomposers (bacteria or fungi).
What do decomposers secrete?
Enzymes to break material into smaller soluble food molecules.
What are the 3 factors that affect decomposition rate?
Temperature
Water availability
Oxygen availability
How does temperature affect decomposition?
Warmer = faster reactions, but too hot = enzymes denature, stops decomposition.
Why does water affect decomposition?
Needed for respiration and makes food easier to digest.
Why is oxygen important for decomposition?
Most decomposers respire aerobically.
What is compost?
A product of decayed biological material, used as natural fertiliser by farmers.
How is compost made faster?
By providing oxygen (aerobic respiration produces heat) and raising temperature.
Increase in temp means increased rate of decay so compost made quicker
What is the first organism in a food chain?
A producer (e.g., green plant or algae).
What do producers make and how?
Glucose via photosynthesis.
What is the first consumer in a food chain called?
Primary consumer.
What are secondary and tertiary consumers?
Secondary = eat primary.
Tertiary = eat secondary; food chains usually don’t go beyond this.
What does a stable community show?
Population cycles between predators and prey.
What happens when prey population increases?
Predator population increases too
What happens after predators increase due to increase in prey?
Prey population decreases due to more consumption by predators
What happens when prey becomes scarce?
Predator population decreases → prey population rises again.
What is a species?
A group of similar organisms that can breed and produce fertile offspring.
What is a habitat?
The place where an organism lives.
What is a population?
All the organisms of one species in a habitat.
What is a community?
Different populations living and interacting in the same habitat.
What is an ecosystem?
A community and its interaction with non-living (abiotic) parts of the environment
What is an abiotic factor?
A non-living factor that affects organisms.
What is a biotic factor?
A living factor that affects organisms.
Name 4 abiotic factors that affect communities.
Light intensity
Temperature
Moisture levels
Soil pH and mineral content
How does light intensity affect communities?
Required for photosynthesis → affects rate of plant growth → affects food/shelter for other organisms
How does temperature affect communities?
Influences rate of photosynthesis.
How does moisture level affect communities?
Both plants and animals need water to survive.
How does soil pH and mineral content affect communities?
Affects rate of decay (how fast mineral ions return to soil) and nutrient availability for plants.
Why do different plants grow in different soils?
Because of varying nutrient concentrations.
Name 4 biotic factors that affect communities.
Food availability
New predators
New pathogens
Competition
How does food availability affect population size?
More food = more breeding success → population increase.
Why are new predators a threat?
They reduce population sizes by consuming prey.
Why are new pathogens a threat?
Population has no resistance = population can be wiped out quickly.
How does competition affect populations?
Better-adapted species outcompete others, leading to decline in lesser-adapted species.
What is competition in biology?
Organisms compete for resources they need to survive.
What might plants compete for?
Light, space, water, mineral ions.
What might animals compete for?
Space, food, water, mates.
What is interdependence?
How organisms depend on others for vital services (food, shelter, pollination, seed dispersal).
How can adding/removing species affect a community?
Changes prey or predator numbers → affects population balance.
What is a stable community?
All abiotic and biotic factors are balanced; population sizes remain fairly constant.
Why are stable communities difficult to replace?
When lost, their balance of conditions and organisms is hard to restore.
Give examples of stable communities.
Tropical rainforests, oak woodlands, coral reefs.
What are trophic levels?
The stages in a food chain.
What is Level 1 in a food chain and what does it include?
Producers – e.g., plants and algae that make food by photosynthesis.
What is a primary consumer?
An organism that eats producers – usually herbivores.
What is a secondary consumer?
An organism that eats primary consumers – usually carnivores.
What is a tertiary consumer?
An organism that eats other carnivores – top predators.
What are apex predators?
Tertiary consumers that have no predators.
What do pyramids of biomass show?
The relative biomass at each trophic level.
What does each level of a pyramid of biomass represent?
The relative weight of material at each level.
What happens to biomass as you move up trophic levels?
It decreases.
Why is biomass higher at the bottom of the pyramid?
Because not all food is converted to biomass in consumers.
How much energy from sunlight do producers transfer to biomass?
About 1%.
Why is only 10% of biomass passed on to the next level?
Most biomass is lost due to respiration, waste products, or being inedible
Give 3 reasons why not all biomass is transferred.
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.
Why can biomass be lost as faeces?
Herbivores don’t digest all material they eat.
What is the formula for efficiency of biomass transfer?
(Biomass transferred to the next level ÷ Biomass available at the previous level) × 100
Why are there fewer organisms in higher trophic levels?
Because less biomass is transferred each time.
What is egestion?
waste products that cannot be digested (eg teeth of prey) removed by faeces
What is excretion?
Waste products produced by the body removed through excretion eg urea thru urine
