Energy Flow
What is the ultimate source of energy in most ecosystems?
sun
What is a trophic level?
Position in a food chain
What is population?
Group of organisms of one species in the same area at the same time
Name one nutrient cycle.
Carbon cycle / nitrogen cycle
A population of rabbits shows different fur colours.
What is this an example of?
variation
What process allows producers to convert light energy into chemical energy?
Photosynthesis
What is the difference between a food chain and a food web?
Chain = single pathway; web = interconnected chains
Name two factors affecting population size.
Food, predators, disease, space
What is decomposition?
Breakdown of dead organisms by microorganisms
Two identical twins have slightly different weights as adults.
What type of variation does this show?
Why is energy lost at each trophic level?
Heat loss (respiration), movement, waste
What is a producer and give an example.
Makes own food (e.g. plant)
Explain why population growth is initially rapid and then slows.
Resources become limiting; competition increases
Explain the role of bacteria in the nitrogen cycle.
Nitrogen fixation, nitrification, denitrification
A species has very little genetic variation.
Predict what is likely to happen if the environment suddenly changes.
Population may not survive / extinction risk / cannot adapt
Explain why pyramids of energy are always upright.
Energy decreases at each level; cannot increase due to loss
Explain why organisms can appear in more than one trophic level in a food web.
Omnivores feed at different levels
What is the limiting factor of the population size in Lag Phase?
the number of population itself.
Explain why nutrients must be recycled in ecosystems.
Limited supply; needed for growth; reused by organisms
2 differences between natural and artificial selection!
done by human - done by nature/naturally; slower - faster; increase genetic variation - decrease genetic variation.
A farmer decides to feed crops directly to humans instead of feeding them to animals first.
Explain why this is more energy efficient, using your knowledge of energy transfer in food chains.
Fewer trophic levels means less energy loss → more energy available to humans - supports more people / higher yield
Explain how removing one species can affect the entire food web.
Disrupts predator-prey relationships; population imbalance
Explain how limiting factors control population size.
Reduce growth rate; increase death rate or decrease birth rate
Mention any carbon sinks on earth?
A population of insects is exposed to a pesticide.
After several generations, most are resistant.
Explain how this change occurs, starting from variation in the population.
Genetic variation exists (mutation), some insects resistant, non-resistant die, resistant survive & reproduce, allele frequency increases.