ECOSYSTEMS YEAR 8

• Food chain


  A list of organisms in a habitat that shows their feeding relationship, i.e. what eats what. The organisms are joined by arrows which show the transfer of energy in food between them.
• Simple food chain with three trophic levels

  • Fox
  • Rabbit
  • Grass
• Producer


  • Usually a green plant or algae that completes photosynthesis to store energy from sunlight as glucose
• Prey


  Animals that are hunted and eaten
• Predator


  Consumes prey
• Top (or apex) predator


  Final consumer at the top of the food chain that is not eaten by anything else
• Most populations of organisms that live in a habitat usually have more than one food source. They usually consume more than one organism from the trophic level below. This means that there are almost always more than one food chain and these are interlinked into a food web.
• Mercury accumulation in the food chain

  1. Tiny animals and plants called plankton absorb mercury compounds

  2. When plankton are eaten by small fish, the mercury they contain stays in the fish

  3. Larger fish eat the small fish, and larger ones still (such as tuna fish) eat them

  4. This creates a high concentration of mercury in the tuna
• People eating contaminated tuna may get mercury poisoning. Mercury is now banned from many chemical products and mercury use in industry is carefully regulated.
• Factors affecting population size in an ecosystem

  • Competition between organisms for resources
  • Predator numbers
  • Disease
• All living things within an ecosystem are interdependent. A change in the size of one population affects all other organisms within the ecosystem. This is shown particularly clearly by the relationship between predator and prey populations.
• Respiration is a chemical reaction which occurs in all living cells, releasing energy from glucose.
• Aerobic respiration


  Occurs with oxygen and releases more energy but more slowly
• Anaerobic respiration


  Occurs without oxygen and releases less energy but more quickly
• Respiration is not breathing. That is called ventilation. Respiration is a chemical reaction which occurs in every one of the cells in the human body. It releases energy stored in glucose and without it, these cells would die.
• Aerobic respiration


  Glucose + oxygen -> carbon dioxide + water
• Aerobic respiration slowly releases lots of energy stored in It glucose .breaks down glucose and combines the broken down products with oxygen, making water and carbon dioxide. The carbon dioxide is a waste product of aerobic respiration because cells do not need it.

  
  

  Aerobic and anaerobic respiration - OCR 21st Century - BBC
• 'Aerobic' does not mean 'in air' even though they sound the same. It means 'in the presence of oxygen.'
• A food web shows how different species are interconnected by feeding relationships
• Ecosystem key words


  • co-exist
  • community
  • oak tree
  • woodlice
  • habitat
• Ecosystem


  The name given to the plants and animals that are found in a particular location, and the area which they live. The plants and animals depend on each other to survive.
• Community


  The organisms in an ecosystem
• Habitat


  The area the organisms in an ecosystem live in
• Co-exist


  The plants and animals in a community live in the same place at the same time
• Niche


  A particular place or role that an organism has within an ecosystem
• Photosynthesis


  1. Leaf absorbs carbon dioxide from air through stomata

  2. Leaf absorbs water from soil through root

  3. Leaf uses energy from sunlight to transform water and carbon dioxide to glucose and oxygen
• Interdependence means the way in which living organisms depend on each other to survive, grow, and reproduce
• Organisms in a food web depend on each other for survival. They are interdependent
• Population


  The number of animals or plants of the same type that live in the same area
• The population size of one type of organism


  Has a direct effect on the size of another type of population
• In this food web, the rabbit has one predator. Its predator is a fox
• If the number of rabbits decreases due to a disease


  The number of foxes would also decrease as they would have less to eat
• In this food chain, the algae is the producer. The area is polluted with toxic waste
• The algae each contain high levels of toxins
• The nymphs eat lots of algae. The fish eat lots of nymphs
• The herons eat a lot of fish
• Bioaccumulation


  The levels of toxins build up through the food chain because the bigger organisms eat lots of the smaller organisms
• The herons consume high levels of toxins
• Photosynthesis


  1. Reactants: carbon dioxide, water, light

  2. Products: glucose, oxygen
• The leaf absorbs carbon dioxide from the air through the stomata and absorbs water from the soil through the root. Then it uses energy from the sunlight to transform the carbon dioxide and water into the products of oxygen and glucose.