BS

Chapter 4 - Ecosystems

Ecology

  • Branch of biology that deals with the relations between organisms and their surroundings.
  • Biological Populations and Communities
    • Organisms that look similar in genetic makeup, chemistry and behavior belong to the same species.
    • Organisms of the same species that occupy a specific area are a population.
    • Populations of different species makes a community
    • An ecosystem is formed by the interaction of a community of organisms with their physical environment.
    • These make up the biosphere.
  • Population Dispersal Patterns
    • Populations can be dispersed in 3 ways
    • Clumped
    • Dense with organisms in some communities.
    • When resources become scarce, organisms clump together to get those resources.
    • Random
    • Little interaction between organisms.
    • Usually in places consistent with environmental conditions and resources.
    • Uniform
    • Uniform spacing between individuals.
    • Usually arises from competition between resources.
  • Ecological Niches
    • Area within a habitat occupied by an organism and includes the function of that organism within an ecological community.

Law of Tolerance

  • States that the existence, abundance, and distribution of species depends on the tolerance level of each species to both chemical and physical factors.
  • Limiting Factors
    • Abiotic factor that limits or prevents the growth of a population.
  • Resource Partitioning
    • Resources in an environment are limited.
    • Some species have evolved to share a certain resource.
    • Spatial Partitioning - where the competing species use the same resource by occupying different areas within the range of the resource.
    • Morphological Partitioning - Where they share the species, but have evolved different structures to use the resources differently.
  • Interactions between species
    • Amensalism - One species suffers, while the other species is not affected.
    • Commensalism - One species benefits, while the other species is not affected.
    • Competition - Prominent in predator-prey relationships.
    • Mutualism - Two species benefit
    • Parasitism - One species benefits, the other is harmed.
    • Predation - Predators hunt and kill prey.
    • Saprotrophism - Obtain nutrients from dead or decaying plants.
  • Keystone Species
    • A species that contributes to a diversity of life and whose extinction would lead to an extinction of multiple species.
  • Edge Effects
    • How a local environment changes along some type of boundary or edge.

Energy Flow

  • The ultimate source of energy is the sun. Plants use the sun to produce food.
  • Photosynthesis
    • Plants remove carbon dioxide from the atmosphere using photosynthesis.
    • Plants capture light through chlorophyll.
    • Oxygen is released into the atmosphere during photosynthesis.
  • Cellular respiration
    • Organisms that rely on autotrophs are called heterotrophs.
    • Cellular respiration is the opposite of photosynthesis.
    • Glucose in the cells will result in carbon dioxide, water, and chemical energy to be produced.
  • Ecological Pyramids and 10% rule
    • During the transfer of energy from one trophic level to the other, only 10% of energy is transferred.
    • The rest of the energy is lost in the form of heat, metabolic processes, and so on.
  • Ecosystem Productivity
    • Of all sunlight that reaches earth, 3% for land plants, and <1% are used for aquatic plants.

Biomes

  • Biomes
    • Biotic Community characterized by the dominant forms of plant life and the climate.
    • Temperature and precipitation are determinants of biomes.