Population Dynamics and Ecosystem Interactions

This video is part of an IGCSE Biology revision series, focusing on organisms and their environment. It covers key definitions such as ecosystems, food chains, and trophic levels. The video explains energy flow in ecosystems, highlighting the role of producers and consumers, and the concept of energy loss at each trophic level. It discusses food webs and pyramids, including the pyramid of numbers and biomass. The video also explores population growth stages and factors affecting it, such as food supply and predation. The session concludes with a preview of the next video on nutrient cycles.

What is the main focus of the first video in the series on organisms and their environment?

• Climate change effects

• Organisms and their environment

• Nutrient cycles

• Human impact on ecosystems

Which term describes a community of interdependent organisms and their environment?

• Food chain

• Ecosystem

• Trophic level

• Decomposer

What is the primary source of energy input into a biological system?

• Chemical energy

• Heat energy

• Sunlight

• Kinetic energy

In a food chain, what percentage of energy is typically transferred from one trophic level to the next?

• 10%

• 25%

• 90%

• 50%

Why is it more energy-efficient for humans to consume plants directly rather than animals that eat plants?

• Plants are more abundant

• Energy is lost at each trophic level

• Animals are harder to digest

• Plants have more nutrients

What does a pyramid of numbers represent in an ecosystem?

• The biomass of organisms

• The energy flow between trophic levels

• The diversity of species

• The number of organisms at each trophic level

Which phase of population growth is characterized by exponential growth under ideal conditions?

• Decline phase

• Stationary phase

• Log phase

• Lag phase

What is the carrying capacity in the context of population growth?

• The maximum growth rate

• The population size that can be supported by the environment

• The initial population size

• The number of species in a community

Which factor is NOT mentioned as affecting population growth?

• Food supply

• Predation

• Climate change

• Diseases

What happens during the decline phase of population growth?

• Population size decreases significantly

• Population size fluctuates unpredictably

• Population size increases rapidly

• Population size becomes stable