ecology

• carbon cycle

  the constant recycling of carbon through the processes of life, death and decay
• water cycle

  a series of processes that circulate water through the environment
• food chain

  the feeding relationships between organisms
• producer

  an organism that can make its own food
• predator

  an animal that hunts, kills and eats other animals [prey]
• prey

  an organism that is hunted and killed by a predator for food
• apex predator

  the top consumer in a food chain; has no predators
• biodiversity

  the variety of living organisms and the ecosystems in which they live
• pollution

  the contamination of an environment

  eg

  by chemicals or gases
• acid rain

  rain with a low pH [acidic] due to the gases released by burning fossil fuels
• deforestation


  the destruction of trees by cutting down large areas of trees
• global warming 


  the increase in the average temperatures on earth due to a rise in the levels of greenhouse gases in the atmosphere
• feeding relationships


  all food chains begin with a producer, which synthesises [makes molecules].

  the producer is usually a green plants.

  producers are eaten by primary consumers who are then eaten by a tertiary consumer
• a primary consumer = herbivore

  a secondary consumer = carnivore

  tertiary consumer = omnivore
• consumers that eat other animals are called predators and those that are eaten are called prey
• top consumers are called apex predators

  they are apex predators

  they are carnivores or omnivores with no predators
• in a stable community the numbers of predators and prey rise and fall in cycles
• a high biodiversity helps eco systems to be stable as species depend on each other for food and shelter.
• the future of humans relies on maintaining a good level of biodiversity
• factors that put biodiversity at risk and affect the distribution of species in an ecosystem include changes in:

  • availability of water
  • temperature
  • atmospheric gases
• scientists and government have taken steps to help maintain biodiversity these include:

  • setting up breeding programs for endangered species
  • protecting rare habitats eg coral reefs
  • encouraging farmers to keep margins and hedgerows in fields
  • reducing deforestation and carbon dioxide emissions
  • recycling resources rather than dumping waste in landfill
• adaptations

  cactus adaptations:

  • needles instead of leaves reduce water loss
  • thick stem stores water
  • extensive root system to take in water
• communities can be affected by biotic or abiotic factors

  biotic = living factors eg availability for food and new predators and new pathogens

  abiotic = non-living factors eg light intensity and temperatures and moisture levels
• organisms have adaptations that enable them to survive in the conditions in which they normally live

  these adaptions could be

  1. structural
  2. behavioral
  3. functional
• extremophiles

  organisms that live in very extreme environments eg

  high temperatures

  pressure

  salt concentration
• ecosystem

  all the organisms hat live in a habitat and the non-living parts of the habitat
• competition

  the interaction between organisms striving for the same resources
• interdependence

  when one organism relies on another for certain resources
• adaptation

  the gradual change in a particular organism, over many generations, to become better suited to its environment
• population

  a group of organisms of the same species living in a habitat
• transect line 


  a fixed line along which populations are sampled
• quadrat 


  a square frame (usually between 0.25m2 and 1m2) used for sampling organisms in their natural environment
• the formation of gametes involves meiosis, when a cell divides by meiosis:

  • copies of the genetic information are made
  • the cell divides twice to form four gametes, each with a single set of chromosomes
  • all gametes are genetically different from each other
• meiosis is important because it halves the number of chromosomes in gametes.

  This means that fertilisation can restore the full number of chromosomes.
• cell with two pairs of chromosomes (diploid cell).

  each chromosome replicates itself.

  chromosomes part company and move to opposite poles.

  cell divides for the first time.

  copies now separate and the second cell division takes place.

  four haploid cells (gametes), each with the half the number of chromosomes of the parent cell.
• sexual reproduction


  involves the fusion (joining) of males and female gametes:

  1. sperm and egg cells in animals
  2. pollen and egg cells in flowering plants.

  this leads to a mix of genetic information, which produces variation in the offspring.

  sperm + egg = fertilised egg cell

  23 chromosomes + 23 chromosomes = 46 chromosomes, half from the mother and half from the father
• asexual reproduction

  1. only one parent.
  2. no fusion of gametes, so no mixing of genetic information.
  3. the production of genetically identical offspring (clones).
  4. mitosis

  many plants reproduce asexually and in different ways

  eg

  strawberry plants send out long shoots called runners, which touch the ground and grow a new plant.
• genetic engineering


  ^ is a more recent way of bringing about changes in organisms.

  it involves changing the characteristics of an organism by introducing a gene from another organism.
• genetically modified (GM) 


  ^ plant crops have been genetically engineered to:

  1. be resistant to diseases, insects, or herbicide attack.
  2. produce bigger, better fruits.

  fungi or bacterial cells have been genetically engineered to produce useful substances, eg

  human insulin to treat type 1 diabetes.
• selective breeding 


  used to produce food crops from wild products and to produce domesticated animals from wild animals

  it is the process by which humans breed plants and animals with particular, desirable genetic characteristics