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Populations & communities


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Populations & communities

  1. 1. Populations & Communities
  2. 2. A population is a group of individuals of one species that interbreed together in a particular living place. Members of the one species have the capacity to interbreed and produce fertile offspring.
  3. 3. The community represents all of the living organisms found living together in a particular area or habitat.
  4. 4. The ecosystem represents the sum of all organisms living in a particular area, along with the habitat and the physical component of the environment that affects organisms.
  5. 5. Physical factors include Oxygen levels Carbon dioxide levels Water availability Sunlight Soil characteristics
  6. 6. A particular community will usually have a variety of populations of organisms – including producers, consumers and decomposers Populations in the community interact with one another in a variety of ways Competing for resources Hunting or killing prey Symbiotic relationships
  7. 7. Producers Mainly consist of photosynthetic organisms Consumers Feed on others to obtain essential requirements Decomposers Feed on dead and decaying material, recycling essential elements
  8. 8. Competition Organisms which compete for the same resources E.g. light, space, oxygen, and food. Predation Where one organism feeds on or eats another live organism Predation shapes the community and affects the number or biodiversity of the community
  9. 9. Plant defense against Predation Physical Thorns, spikes, hair, waxy or silica secretions Chemical Some plants produce chemicals that deter herbivores from eating them
  10. 10. Animal defense against Predation Chemical Poison from snakes , spiders, bees, wasps etc. Colouration Camouflage is used to hide themselves i.e. grasshoppers Some species use mimicry – mimic the appearance of another species which does have protection
  11. 11. Symbiosis Symbiotic relationships exist between organism of two different species Mutualism A relationship where both species benefit E.g. Algae (photosynthesis) and fungi (moist environment) Bacteria in the stomach of a cow which breaks down cellulose
  12. 12. Commensalism One species benefits and the other species remains unharmed E.g. Barnacles attach themselves to shellfish etc. acting as filter feeders but do no harm
  13. 13. Parasitism The prey is harmed or eaten by an organism that is smaller than it is. E.g. Parasites include lice, ticks, fleas
  14. 14. Both benefit One benefits, neither is harmed One benefits, the other is harmed Parasitism x Mutualism x Commensalism x
  15. 15. Hierarchy of Classification Kingdom Animal Phylum Chordata Class Mammalia Order Primate Family Hominidae Genus Homo Species Homo sapiens
  16. 16. Mechanisms that maintain reproductive isolation Members of the one species have a unique gene pool or total set of genes in the species. A biological feature that prevents gene flow between two closely related species, even though the groups habitats may overlap.
  17. 17. Reproductive barriers form isolating boundaries around closely related species Barriers that prevent fertilisation  Different mating calls  Use of species specific chemicals to attract members of the opposite sex  Different in flower shape or genitalia  Different seasons or times for reproduction  Inability of sperm to survive in the reproductive tract  Pollen tube unable to grow towards the ovules
  18. 18. Barriers that prevent the development of fertile adults Zygotes fail to develop Young fail to reach sexual maturity Offspring are infertile
  19. 19. There are two types of nutrition that organisms use to obtain their essential requirements: Autotrophs or Producers can make their own food from inorganic materials Heterotrophs (herbivores, carnivores or omnivores) need to feed on others to obtain their nutritional requirements
  20. 20. Trophic levels in a community represent the feeding levels or trophic structure of the community Producers trap the Sun’s energy and are autotrophs Consumers feed on others to obtain their nutrition Decomposers break down dead material to obtain their essential requirements
  21. 21. Food Chain