Ecology

• Competition is a type of ecological interaction where two or more organisms compete for the same limited resources.
• Energy from sunlight enters living organisms through photosynthesis in green plants, known as producers
• Organic food molecules produced by plants are passed on to consumers through food chains
• A food chain is a diagram showing the flow of food and energy from one organism to the next
• Plants are producers because they produce their own food
• Consumers are organisms that consume producers and other organisms
• Decomposers feed on dead organic matter
• Types of consumers:

  • Herbivores: consume plants or plant material only
  • Carnivores: eat animals or animal material only
  • Omnivores: consume both animal and plant materials
• Each organism in a food chain represents a trophic level
• Trophic level refers to the position an organism occupies in a food chain
• The number of trophic levels in a food chain is limited to four or five
• Animals show predator-prey relationships

  • Predators are carnivores that feed on other animals called prey
• Food chains are interrelated to form food webs
• All living organisms eventually die and decomposers and detritivores obtain food from dead organisms
• Decomposers include bacteria and fungi, they break down dead plant and animal material into humus
• Detritivores feed on small fragments of dead material, called detritus, e.g. woodlice and earthworms
• Decomposers and Detritivores are all Saprophytes
• Symbiosis describes relationships where different species of organisms live together
• Three types of symbiosis:

  • Mutualism: both organisms benefit
  • Commensalism: one benefits without harming the other
  • Parasitism: one organism benefits at the expense of the other
• Parasites live and feed on or inside another organism, called the host
• Two types of parasites:

  • Ectoparasites: live on the outer surface of the host, e.g. ticks, lice, fleas
  • Endoparasites: live within the host, e.g. plasmodium causing malaria, tapeworms
• Mutualism is a type of ecological interaction where both organisms involved benefit from their relationship.
• Predation is a type of ecological interaction where one organism (predator) hunts and kills another organism (prey) for food.
• Parasitism involves an animal living on or inside another (the host) without killing it but still benefiting from its presence.
• Symbiosis refers to any close association between different biological entities, including mutualistic relationships such as pollination by bees and seed dispersal by birds.
• Commensalism is an ecological interaction where only one organism benefits while the other is not harmed.
• An example of commensalism is remora fish attaching themselves to sharks using suction cups, benefiting from food scraps left behind but not harming the shark.
• All living organisms depend directly and indirectly on plants for food, as plants are the only organisms capable of producing their own food
• Energy transfer in food chains:

  • Not all energy from organic food molecules made by green plants during photosynthesis is passed along a food chain
  • Some energy is used and lost at each trophic level
• Energy is lost by:

  • Growth
  • Respiration
  • Stored
  • Excreted
  • Heat
  • Death
• Diagrams called ecological pyramids show how energy moves through ecosystems
• Pyramid of Numbers:

  • Shows the numbers of individual organisms at each trophic level
  • The width of each bar is proportional to the number it represents at each trophic level
• Pyramid of Biomass (dry mass of living material):

  • Shows the biomass of each organism at each trophic level
• Pyramid of Energy:

  • Pyramid of numbers and pyramid of biomass give a snapshot at a moment in time
  • Pyramid of energy is determined over time
  • Shows the rate at which energy flows through a trophic level
• Pesticides can spread through the environment via a food chain
• Pesticides (e.g., fungicides, herbicides, insecticides) are toxic chemicals to some organisms
• Bioaccumulation is the gradual accumulation of substances (e.g., pesticides) in an organism
• Bioaccumulation occurs when an organism absorbs a substance faster than it is lost or eliminated by catabolism and excretion