Unit 3

• What is a population in ecological terms?

  A group of organisms of one species
• What is a niche?

  The role an organism plays in its ecosystem
• What defines a species?

  A group of organisms that can interbreed to produce fertile offspring
• What does the term biodiversity mean?

  The variety of living things
• What are the two types of competition in ecosystems?

  • Intraspecific: Competition among individuals of the same species
  • Interspecific: Competition among individuals of different species
• What is the equation for an ecosystem?

  Habitat + community = ecosystem
• Why might a pyramid of numbers have an irregular shape?

  There may be a large number of parasites at the top of the food chain, or one tree at the bottom level
• What are the different types of consumers in an ecosystem?

  • Producer: Makes its own food through photosynthesis
  • Primary consumer: Eats only plant material (herbivore)
  • Secondary consumer: Eats only animal material (carnivore)
  • Tertiary consumer: Top predator, eats both plant and animal material (omnivore)
• What are three ways energy can be lost from a food chain/web?

  Heat, movement, and undigested materials
• What does a herbivore eat?

  Only plant material
• What does a carnivore eat?

  Only animal material
• What does an omnivore eat?

  Both plant and animal material
• What is the function of producers in an ecosystem?

  Producers make their own food through photosynthesis
• What is the role of a tertiary consumer?

  It is the top predator in the food chain
• What is the role of a primary consumer?

  It eats only plant material
• What is the role of a secondary consumer?

  It eats only animal material
• What is the fate of by-products formed in stage I of an ecosystem?

  They are needed for stage II
• What is the significance of CO2 in ecosystems?

  It is a by-product of respiration and is used in photosynthesis
• What is the role of hydrogen in ecosystems?

  It is a component of water and organic molecules
• What is the name of the green pigment that captures light energy in photosynthesis?

  Chlorophyll
• What is the site of photosynthesis in plant cells?

  Chloroplast
• What are the two substances produced in stage 1 of photosynthesis?

  ATP and NADPH
• What is the byproduct formed in stage 2 of photosynthesis?

  Oxygen
• What is the function of ATP in stage 2 of photosynthesis?

  Provides energy to produce glucose
• What is carbon fixation in the context of photosynthesis?

  The process of converting carbon dioxide into organic compounds
• What are the three factors that can limit the rate of photosynthesis?

  Light intensity, carbon dioxide concentration, and temperature
• What are the products of photosynthesis and their uses?

  • Glucose: Provides energy and can be converted into:
  • Starch (storage carbohydrate)
  • Cellulose (structural carbohydrate)
  • Oxygen: Released as a byproduct
• What happens during stage 1 (Light-dependent stage) of photosynthesis?

  Light energy is converted into chemical energy in the form of ATP and NADPH
• How does the process of photosynthesis contribute to the energy needs of plants?

  Photosynthesis converts light energy into chemical energy stored in glucose
• What is the role of stomata in photosynthesis?

  Stomata allow the exchange of gases, including the intake of carbon dioxide and release of oxygen
• What does the term "variation" mean in simple words?

  Variation refers to differences among individuals in a population
• What are the steps involved in the light-dependent reactions of photosynthesis?

  1. Light absorption by chlorophyll

  2. Water splitting to release oxygen

  3. Production of ATP and NADPH
• What are the steps involved in the Calvin cycle (light-independent reactions) of photosynthesis?

  1. Carbon dioxide fixation

  2. Reduction of fixed carbon

  3. Regeneration of RuBP

  4. Glucose synthesis
• What is biological control?

  Using natural predators to control the population of an organism
• Give an example of biological control.

  Ladybirds to control greenfly population
• What do fertilizers provide to crops?

  Chemicals such as nitrates
• What is the purpose of fertilizers?

  To increase crop yield
• What are two alternatives to using pesticides?

  Biological control and GM crops
• What are genetically modified (GM) crops?

  Crops derived from GM organisms with specific changes in their DNA
• Why might GM crops be described as more environmentally friendly than conventional crops?

  They can be resistant to pests and drought, reducing the need for pesticides and irrigation