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.

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