Structure and distribution os terrestrial biomes are controlled by climate and distrubance
8 terrestrial biomes:
- Temperate grassland
- Temperate broadleaf forest
- Coniferous forest
- Tropical rainforest
Aquatic biomes are classified into freshwater biomes and marine biomes.
- Characterized by grasses and some trees
- Dominant herbivores: insects, such as ants and termites
- Dominant abiotic factor: fire - many plants are adapted for fire
- Plant growth is substantial during rainy season
- Large grazing mammals must migrate during regular seasons of drought
- Sparse rainfall
- Desert plants and animals are adapted to absorb and store water
- Contains many CAM plants and plants with adaptions that prevent animals from consuming them
- Temperature (either hot or cold) is usually very extreme
- Dominated by dense, spiny, evergreen shrubs
- Coastal areas with mild, rainy winters and long, hot, dry summers
- Plants adapted to fires
- Marked by seasonal drought with occasional fires
- Has large grazing mammals
- These factors prevent seasonal growth of trees
- Soil is rich in nutrients which makes it good for agriculture
Temperate Broadleaf Forest
- Marked by dense strands of deciduous trees that requires sufficient moisture
- More open than rainforests
- Stratified-top layer has 1-2 strata of trees; beneath are shrubs; under that is herbaceous stratam
- Dominated by cone-bearing trees such as pine, fir, and spruce
- Shape of conifers prevents much snowfall from accumulating on the tree's branches
- Marked by permafrost (permanently frozen layer of soil)
- Very cold temperatures
- High winds
- Little rainfall
- Supports no trees or plants
- Accounts for 20% of Earth's terrestrial surface
- Pronounced vertical stratification
- Dense canopy; so little light breaks through
- Marked by epiphytes, plants that grow on other plants instead of soil
- Varied rainfall
- Greatest biodiversity of all terrestrial biomes
- Make up the largest part of the biopshere
- Biomes are classified as freshwater and marine biomes
- All aquatic biomes display vertical stratification, which leads to:
- Photic zone - there is enough light for photosynthesis to occur
- Aphotic zone - very little light penetrates
- Benthic zone - bottoms of biome; made up of sand, inorganic matter, and organic sediments
- Thermoclines - narrow layer of fast temperature change that separate a warm upper layer of water and cold, deeper water
- 2 types of freshwater:
- Standing bodies of water (lakes and wetlands)
- Moving bodies of water (streams and rivers)
- In lakes, communities are distributed according to water depth.
- Oligotrophic lakes - deep lakes that are nutrient-poor, oxygen-rich, and contain sparse plankton
- Eutrophic lakes - shallow lakes that are nutrient-rich, oxygen-poo, and high phytoplankton concentration
- In streams and rivers, organisms are distributed in vertical zones and from headwaters to the mouth.
- Intertidal zone - land meets water, is periodically submerged and exposed by the twice-daily tides
- Necrotic zone - shallow water over the continental shelves
- Pelagic zone - vast realm of open blue water
- Coral reef - a biome created by a group of cnidarians that secret hard calcium carbonate shells; the most productive ecosystems on earth
Fundamental Characteristics of a Population
Density - number of individuals per unit area or volume
Dispersion - pattern of spacing among individuals within the boundaries of the population
Demography - study of vital statistic of a population, especially birth and death rates
- Type I - low death rates during early and midlife, then the death rate increases sharply in order age groups
- Type II - constant death rate over the organism's life span
- Type III - very high early death rates, then a flat rate for the few surviving to older age groups
K & R Selection
K-selection - selection of life history traits that are sensitive to population density and carrying capacity
r-selection - selection for life history traits that maximize reproductive success
Interspecific Competition ( - / - )
Occurs when resources are in short supply. These two concepts are the central idea of competition and community structure:
- The competitive exclusion principle states that when two species are competing for resource, the one with the reproductive advantage will eventually eliminate the other
- An ecological niche is the total of biotic and abiotic resources that a species uses. Fundamental niche is the niche potentially occupied by the species, while realized niche is the portion of the fundamental niche the species actually occupies.
Herbivory ( + / - )
A herbivore eats part of a plant or alga. A plant's main defenses are chemical toxins, spines, and thorns.
The feeding relationships among organisms.
Trophic levels - links in the trophic structure of a community
Changes a community by removing organisms or changing resource availability (e.g. storm, fire, flood, drought, human activity). The intermediate disturbance hypothesis states that moderate levels of disturbance fosters greater species diversity than low or high levels of disturbance.
Ecological succession - transitions in species composition in a certain area over a period of time
- Primary succession - a virtually lifeless area with no soil gradually fosters plants and animals (e.g. a new volcanic island)
- Secondary succession - an existing community has been cleared by a disturbance, leaving the soil intact
Flow of Energy
Primary producers - autotrophs ("self-feeders"); support all other organisms in the ecosystem
Heterotrophs - eat other organisms
- Herbivores - consume primary producers (primary consumer)
- Carnivores - consume other heterotrophs (secondary or tertiary consumers)
- Detritivores (Decomposers) - consumers get energy from nonliving organic material
Amount of light energy converted to chemical energy by autotrophs
- Gross Primary Production (GPP) - total primary production of an ecosystem
- Net Primary Production (NPP) - primary production minus the energy used by autotrophs in their "autotrophic respiration" (Ra)
NPP = GPP - Ra
The maximum population size that a certain environment can support at a particular time with no degradation of habitat.
A population's growth rate equals birth rate minus death rate.
dN / dT = B - D
Energy is lost at each level of transfer as heat, for movement or reproduction or any life processes that consume energy.
10% of usable energy is passed on to each level. A primary consumer would get 10% of the energy the autotroph had. A secondary consumer would get 10% of the energy the primary consumer had, which is 1% of what the autotroph had.
The loss of energy from trophic level to trophic level is one of the factors that keeps the food chains so short.