Lecture 3

The various biomes and their basic properties as outlined in lecture and in the textbook

Biomes are the broadest classification of terrestrial ecosystems that have similar characteristics due to sharing similar climatic conditions. tropical seasonal forests:drought tolerant forests that look brown and dormant in the dry season but become vividly green during rainy months grasslands:forests with little or no rainfall savanna: a grassland with sparse tree cover Desert: occur where precipitation is rare and unpredictable, usually with less than 30 cm a year chaparral: inhabited by drought tolerant animals Deciduous forest: loses leaves seasonally Coniferous:cone bearing forests Temperate rainforest:a cool, rainy forest often enshrouded in fog boreal forest:northern forests, between 50-60 north and tundra Tiaga:border area between boreal forest Tundra: a treeless landscape, high alt, no more than 3 growing months(even less if artic tundra) alpine tundra: one short and intense growing season

Species interactions of various kinds

Competition Intraspecific competition - competition among members of the same species which can be reduced if: young disperse, exhibiting strong territoriality, resource partitioning between generations Interspecific competition - competition between members of different species Unless there is a clear winner, competition has negative consequences for all competitors Recall that species tend to avoid prolonged competition by resource partitioning PREDATION: A predator is any organism that feeds directly on another organism, whether or not this kills the prey. Example: a parasite feeds on an organism but does not immediately kill it SYMBIOSIS: A prolonged, close interaction between species Mutualism - both organisms benefit from their association (e.g., a fungus and an alga combine to make a lichen) Commensalism - one species benefits while the other neither benefits nor is harmed (e.g., a bromeliad growing on the trunk of a tree absorbs water and nutrients dripping down the tree trunk without harming the tree) Parasitism - a form of predation, is also sometimes considered a symbiosis because of the dependency of the parasite on its host.

Disturbances and succession

DISTURBANCES: A disturbance is any force that disrupts established patterns of species diversity and abundance, community structure, or community properties, e.g., storms, fires, logging. Disturbance tends to disrupt the superior competitors the most and allows less competitive species to persist. Some landscapes never reach a climax community because they are characterized by periodic disturbances (such as wildfires) and are made up of disturbance-adapted species. Many ecosystems are adapted to disturbances and require them to persist. Novel disturbances can result in catastrophic changes to the system SUCCESSION: Succession is the replacement of species in a community by establishment of new species paralleled by replacement or extirpation of old ones. Pioneer species colonize a site that was opened by disturbance. These populations are replaced by intermediate sere species, which are eventually replaced by a climax community. Succession often makes an environment more suitable for life in general, deposits ecological memory Primary Succession-A community begins to develop on a site previously unoccupied by living organisms. Example: A lava flow creates a new land area that is colonized. The first colonists are termed pioneer species. Secondary Succession-an existing community is disrupted and a new one subsequently develops at the site Climax Community-community that develops last and remains the longest

Ecotones: open vs. closed communities and examples

Ecotones -transition areas between adjacent ecosystems Sharp boundaries (edges) - closed communities(power plant in germany) Indistinct boundaries - open communities(an african savannah)

habitat fragmentation vs. core habitat and its effect on edge vs. core habitat. What are edge effects?

Edge effects are a change in species composition, physical conditions, or other ecological factors at the boundary between two ecosystems a core habitat is is an essential habitat for a species Edge effects associated with habitat fragmentation are generally detrimental to biodiversity

What are niches? How are they defined, and how are they related to competition/resource partitioning?

Habitat - the place or set of environmental conditions in which a particular organism lives Ecological niche - Two definitions: Eltonian: The organism's functional role (its response to and effects on its environment) Hutchinsonian: Essentially the set of environmental conditions and interactions required to support a population within an environment Generalists - have a broad niche (brown rat) Specialists - have a narrow niche (giant panda) Competitive exclusion No two species can occupy the same ecological niche at the same time The one that is more efficient at using resources will exclude the other Direct competition is very energy intensive, especially over long periods of time. In many cases, species get around competing directly by partitioning resources/niches amongst each other Resource partitioning - species co-exist in a habitat by utilizing different parts of a single resource. Example: swallows eat insects during the day and bats eat insects at night.

Levels of organization in ecology from species to the biosphere. Know their definitions and differences.

Members of the same species living in the same area that can potentially breed comprise a population. Interacting populations of different species in the same area form a community When we consider the physical environment in addition to the biological community, we talk about an ecosystem. An ecosystem is the minimum level of ecological organization that has all the properties required to sustain life. Large areas of the planet that are dominated by similar ecosystems are sometimes grouped into biomes. The sum of all ecosystems comprises the biosphere - all life on Earth and associated habitats.

Ecosystem productivity. How is it measured, and what are the general geospatial patterns?

Most productive nearest to the equator

Energy flow and matter cycling through ecosystems and their trophic webs

Only 10% of the available energy is passed on to the next level of the trophic web

Photosynthesis - light dependent and light-independent reactions. Respiration.

Photosynthesis converts radiant energy into high-quality chemical energy in the bonds that hold together organic molecules 6 CO2+ 6 H2O --> C6H12O6 + 6 O2 photosynthesis can occur in light independent reactions, via phytoplankton which support a marine food web Humans respire, plants photosynthesize

Ecosystem structure, function, change, and ecosystem services - there is a lot to each of these. Knowing how ecosystems "work" is crucially important to being an environmental scientist, so I expect you to spend quite a bit of time reviewing and understanding these!

Structure: what is there, where is it, how much of it is there? Function: what does "what is there" do, how does "what is there" interact, what are the results of those interactions-energy flow and matter transfer and ecosystem services Change: how ecosystems change structure and function over time-disturbances and recovery Most things in ecology are the result of species trying to minimize the energy expended on competition for scarce resources ECOSYSTEM SERVICES: Ecosystem services are the subset of ecosystem functions which produce outputs that humans directly or indirectly derive a benefit from, In most cases not coupled to the market (essentially FREE in economic sense), Extremely expensive or impossible to pay for replacements, At risk of degradation or destruction when over-used,