Ecology is the study of the interactions between organisms and their environments.

In this chapter – we will focus on:1. The scope of ecology2. Factors affecting the distribution of

organisms3. Aquatic and terrestrial biomes4. The spatial scale of distributions

Abiotic: nonliving environmental factors Biotic: living environmental factors Ecological time: minutes/months/years Evolutionary time: decades/centuries,

etc. Population: group of individuals of the

same species living in a particular area Community: all organisms of all species

that inhabit a particular area Ecosystem: all biotic and abiotic factors

that exist in an area Biosphere: the global ecosystem – sum

of entire planet’s ecosystems

Biogeography: the study of past and present distribution of individual species.

Figure 50.4 – continental drift and barriers such as deserts and mountain ranges all contribute to the distinctive floras and faunas found in Earth’s major regions.

1. Species Dispersal› Species transplants› Introduced species

2. Behavior & Habitat Selection3. Biotic Factors4. Abiotic Factors

Dispersal: the distribution of individuals within geographical population boundaries.

Question: Is the distribution of a species limited by dispersal (i.e. by movement of the organisms)?

› Answer can be obtained by transplant experiments.

If the transplant is successful, then the organisms just haven’t reached the target area.

If the transplant is not successful, then other factors limit the distribution of the organisms, such as competitors, lack of a food source, etc.

Figure 50.6

Humans have moved species around the globe!› Can be deliberate or accidental – but BOTH can be

BAD!› Example: African Honey Bee (pg. 1097)› Example: Zebra Mussel (pg. 1097)

Why do invaders succeed? › New habitat with no natural predators, often unlimited

food supply – potential for rapid population growth. What’s the harm of the invasion?

› out compete native species – disrupt food webs/chains, change ecosystems, kill native species, difficult to control (Kudzu)…the list goes on and on!!!

Not all introduced species thrive in their new environment – many fail to colonize.

The Tens Rule makes the statistical prediction that an average of one out of ten introduced species become established› And…one out of ten established species

become common enough to become pests.

Organisms may not occupy all potentially suitable habitats.  Why?› Evolution doesn’t lead to perfect

organisms.› Evolution is an ongoing process.

Environments change, but it takes a while for organisms to respond.

Organisms that are required for potential community members to colonize may be lacking:› Pollinators, prey, predators that limit

competition, etc.

Figure 50.9 – Researchers test effects of 2 herbivores (sea urchins & limpets) on the abundance of seaweeds.

Both present (red) – no algal cover.Predator-removal demonstrates that sea urchins are main herbivores limiting distribution of the seaweeds.

Temperature› Especially for ectotherms

Water› All living things need water for survival (some

more than others) Sunlight

› Light intensity limits plant growth! Wind

› Increases heat loss & water loss Rocks & Soil

Figure 50.10 – The areas plotted here encompass the range of annual mean temperature and precipitation occurring in the biomes.

Climate & Biomes:

Climate – prevailing weather conditions at a locality.

Microclimate – climate locally varying on a small scale (i.e. on a forest floor or under a rock).

Ponds & lakes are sensitive to seasonal temperature changes› During summer & winter, many lakes in

temperate regions are thermally stratified (layered vertically according to temperature).

› Such lakes undergo biannual mixing of their waters as a result of changing water temp. profiles (called turnover).

› Turnover brings oxygenated water from surface of lakes to bottom and nutrient rich water from bottom of lake to top These events are essential for survival and

growth of organisms at all levels within the ecosystem!

Wetlands Lakes Rivers, streams Intertidal zones Oceanic pelagic biome Coral reefs Benthos

Photic Zone – upper zone; light sufficient for photosynthesis

Aphotic zone – lower zone; little light penetrates Water temperature also stratified

› Colder water is deeper› Oceans (some lakes) have thermocline (narrow layer

that separates the two types of water) Benthic zone – bottom of all aquatic biomes –

sand and inorganic sediments› Organisms that live here are called benthos› Benthos survive on detritus

Standing bodies (lakes, ponds) Moving bodies (rivers, streams) Littoral Zone – regions occupied by floating and

rooted plants; shallow water close to shoreline Limnetic zone – open waters away from shore;

occupied by phytoplankton, zooplankton, fish, etc. Profundal zone – aphotic zone where detritus

accumulates Lakes classified according to production of organic

matter› Oligotrophic lakes – deep and nutrient-poor, sparse

phytoplankton; clearer water› Eutrophic lakes – shallower, nutrient rich, productive

phytoplankton; murky waters result› Mesotrophic – inbetween

Oligotrophic Lake: Nutrient poor, water is clear, oxygen rich; little productivity by algae, relatively deep with little surface area.

Eutrophic lake: nutrient rich, lots of algal productivity so it’s oxygen poor at times, water is murkier often a result of input of agricultural fertilizers

Rivers and Streams: Organisms need adaptations so that they are not swept away by moving water; heavily affected by man changing the course of flow (E.g. dams and channel-straightening) and by using rivers to dispose of waste.

Wetlands: includes marshes, bogs, swamps, seasonal ponds. Among richest

biomes with respect to biodiversity and productivity. Very few now exist as they are thought of often as wastelands. Favor growth of water plants and also rich in invertebrates and birds.

Estuary: Place where freshwater stream or river merges with the ocean. Highly productive biome; important for fisheries and feeding places for water fowl. Often heavily polluted from river input so many fisheries are now lost. Salt marsh grasses, algae, phytoplankton, many invertebrates.

Marine environment with zonation.

Intertidal Zone: Alternately submerged and exposed by daily cycle of tides. Often polluted by oil that decreases biodiversity.

Coral Reefs: occur in neritic zones of warm, tropical water, dominated by cnidarians (corals); very productive, protect land from storms; most are now dying from rise in global temperatures

Neritic zones are shallow regions over continental shelves – beyond intertidal zone.

Deep-sea vent: Occurs in benthic zone; diverse, unusual organisms; energy comes not from light but from chemicals released from the magma.

Tropical rainforest Savannah Desert Chaparral Temperate grassland Temperate deciduous forest Coniferous forest Tundra

Tropical Forest Pronounced vertical stratification Canopy trees make up most o f the upper stratum; little light reaching ground Rainfall is major determining factor in types of plant growth

Savanna Large herbivores and predators Many insects Grasses and scattered trees

Desert sparse rainfall temperature varies – cold at night, hot during day animals and plants adapted to dry climate

Chaparral dense, spiny evergreen shrubs mild rainy winters, long hot summers

Temperate Grassland prairies of N. Amer. are example grasses, herbivores

Temperate Deciduous Forest Deciduous trees Sufficient moisture to support tree growth

Coniferous Forest Cone bearing trees Pacific NW Taiga – Northern Coniferous forests; heavy snowfall during winter

Tundra Permafrost absence of trees little annual rainfall high winds and cold temperatures