Week 6

• ecology


  the study of the interrelationships between living things and their environment (biotic and abiotic)

  • where organisms are found, how many occur there, and why
  • impacts of human beings on natural systems
• individuals


  individual organism in relation to its environment
• populations


  interbreeding members of a single species living in a given place
• communities


  multiple species living and interacting in a given place
• ecosystem


  all the interacting organisms and their non-living environment in a given place
• biome


  distinct biological communities that have evolved in response to similar non-living environments across the Earth
• biosphere


  all life on Earth
• environmental heterogeneity

  the earth is a dynamic (changing), heterogeneous (diverse) environment
• the earth is ___ and the ___ is tilted

  round; axis
• amount of solar energy changes

  seasonally
• predictable change in day ___ and ___

  length; temperature
• biomes


  regions of the Earth with similar environmental conditions and characteristic organismal communities
• plants and animals in a biome are adapted to that particular set of environmental conditions

  temperature and precipitation

  availability of heat and water

  solar energy
• ___ evolution across biomes

  convergent
• plant and animal populations are adapted to local conditions through

  natural selection
• internal body temperature =

  heat gained from environment + heat generated by metabolism - heat lost by environment
• ectotherms


  acquire heat from external sources; have a variable body temperature

  • become active only when warm enough
  • low metabolic rate, don't need to eat often
  • poor oxygen supply, restricted to short bursts of activity
  • poorly insulated, limited optimal range of temperatures
• endotherms 


  acquire heat from internal sources; have more constant body temperature

  • maintain constant body temperature through metabolic heat
  • can maintain high level of energy through aerobic respiration, but need to eat more
  • insulated, can survive at wider temperatures
• life history


  all events in an organism's life, particularly those which influence reproduction

  • mode of reproduction: sexual or asexual
  • when and how often to reproduce
  • number and size of offspring
  • parental care or none
• life history strategies

  strategies have inherent trade-offs for certain characteristics
• opportunistic life history (r-selected)


  favors traits that maximize number of offspring

  adults short-lived, reproduce at an early age, and have many offspring that receive little care

  inhabit unstable/unpredictable environments where resources are not limiting
• equilibrium life history (k-selected)


  favors traits that improve offspring quality

  adults long-lived, late-maturing, produce few offspring that receive extended parental care

  in stable environments with some level of competition
• population


  a group of individuals of the same species inhabiting a given area with potential to interbreed
• population properties are derived from

  the characteristics of individual organisms
• age structure


  proportion of individuals in different age groups and life categories

  • visualized as a pyramid
  • helps to roughly estimate current and future growth
• populations have the capacity to increase indefinitely if


  resources (e.g. space and food) are unlimited
• density-dependent factors


  effects increase as a population grows

  • competition for limited resources like space, nutrients, light
  • stress of crowded conditions reduces birth rate
  • predation increases and disease spreads faster in a larger population
• density-independent factors


  effects unrelated to population density

  • mostly extreme abiotic events: flood, volcanic eruption, severe weather
• at high population densities, we expect

  increased mortality as some individuals do not obtain the resources they need to survive

  decreased fecundity if females delay or defer reproduction because of the lack of resources
• community


  group of interacting populations and species that are found in a given place
• coevolution


  process by which interacting species act as agents of natural selection on one another
• niche


  all the resources a species exploits for its survival, growth, and reproduction; includes habitat, diet, interactions with other organisms as well as abiotic factors where species live such as temperature and water availability
• competition


  interaction between individuals, populations, or species that has negative results for both parties

  • even if one side "wins," it comes at a cost
• intraspecific competition


  between members of own species
• interspecific competition


  between individuals of two species
• competition exclusive principle

  two species that have the exact same niche cannot coexist indefinitely if they are competing for the exact same resources
• resource partitioning

  over long term, competition may cause evolutionary shifts in niche observations of multiple species using the same resource in slighly different ways or at differnt times

  this results in species with similar needs coexisting in the same habitat
• predation


  the consumption of one organism by another

  • true predators kill prey immediately on capture
• predation exerts strong selective pressure on prey to avoid being eaten

  camouflage, warning colors, weapons and structural defenses
• herbivory


  herbivores consume parts of plants, but usually do not kill them