Chapter 50 An Introduction to Ecology and The Biosphere

I. Scope of ecology A. Interactions between organisms and their environment 1. Ecology is the scientific study of the interactions between organisms and their environment. a. Interactions determine distribution and abundance of organisms. b. Three main themes in ecology are: - Where do organisms live? - How many organisms are present? - Why are they located where they are? Figure 50.1 (p. 1093) – Distribution and abundance of the red kangaroo in Australia, based on aerial surveys.

c. Ecology was historically an observational science, often descriptive  natural history. d. An organism’s environment has both abiotic and biotic components. - Abiotic components are nonliving chemical and physical factors such as temperature, light, water, and nutrients. - Biotic components are living factors such as other organisms.

2. Ecology and evolutionary biology are closely related sciences a. Events that occur in the framework of ecological time (minutes, days, years) translate into effects over evolutionary time (decades, millennia). Example: Hawks feeding on mice impact mouse population and may eventually lead to selection for mice with fur as camouflage.

3. Ecological research scale ranges from individuals to the biosphere a. Organismal ecology is about the way in which an individual interacts with its environment. b. Population ecology is the study of a group of individuals of the same species. c. Community ecology deals with all interacting species within a particular area.

d. An ecosystem consists of all abiotic factors plus all organisms that exist in a certain area  Ecosystem ecology. e. Landscape ecology deals with ecosystems that exist within an area and the exchange of energy, material and organisms between these ecosystems. f. The biosphere is the global ecosystem. Global climate research is an example of ecology at the biosphere scale. Figure 50.2 (p. 1094) – Sample questions at different levels of ecology.

II. Factors affecting the distribution of organisms - Biogeography is the study of past and present distribution of individual species. Figure 50.4 (p. 1095) – Biogeographic realms.

A. Species dispersal contributes to the distribution of organisms  Dispersal refers to the process of distribution of individuals within geographic 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.

a. Introduced species sometimes have disasterous impacts: - African honeybee, Zebra mussels Figure 50.7 (p. 1097) – Spread of the African honeybee in the Americas since 1956.

Figure 50.8 (p. 1098) – Expansion of the geographic range of the zebra mussel since its discovery near Detroit in 1988.

B. Behavior and habitat selection contribute to the distribution of organisms 1. Organisms may not occupy all potentially suitable habitat. Why? a. Evolution doesn’t lead to perfect organisms. b. Evolution is an ongoing process. Environments change, but it takes a while for organisms to respond. C. Biotic factors affect distribution 1. Organisms required for potential community members to colonize may be lacking. - Pollinators, prey, predators that limit competition Figure 50.9 (p. 1099, ed. 6; Fig. 50.8, p. 1086, ed. 7) – Predator- removal experiments.

D. Abiotic factors affect distribution 1. Abiotic factors of interest include: - Temperature (range from 0 to 45 C) - Water - Sunlight (water absorbs light, limits area of photysnthesis - Wind (increases heat loss) - Rocks and soil

2. Two important ecological occurrences: a. Seasonal variation  alters temperature and precipitation. Figure (p. 1102) – What causes the seasons?

b. Lake stratification and mixing  alters oxygen and nutrient levels. Dependent on temperature changes and effect on water density. Figure (p. 1104) – Lake stratification and seasonal turnover.

III. Aquatic and terrestrial biomes (Biome = major ecosystem type)  Read and know pages (ed. 6) or pages (ed. 7) with pictures of major biomes

A. Aquatic biomes cover about 75% of the earth’s surface - Wetlands - Lakes - Rivers, streams - Intertidal zones - Oceanic pelagic biome - Coral reefs - Benthos Figure (p. 1106) – The distribution of major aquatic biomes.

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.

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.

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

Deep-sea vent: Occurs in benthic zone; diverse, unusual organisms; such as 1-m long worms energy comes not from light but from chemicals released from the magma.

B. Terrestrial biomes - Tropical forest - Savanna - Desert - Chaparral - Temperate grassland - Temperate deciduous forest - Coniferous forest - Tundra Figure (p. 1112) – The distribution of major terrestrial biomes.

Tropical Forest: Vertical straitification with trees in canopy blocking light to bottom strata. Many trees covered by epiphytes (plants that grow on other plants).

Example of Tropical, Dry Forest

Savanna: Dominate animals are insects (termites and ants). Grasses are dominant plants that are productive in rainy season. Fire during drought is frequent and life is adapted for it, such as migration by large animals.

Desert: Sparse rainfall (< 30 cm per year), plants and animals adapted for water storage and conservation. Can be either very, very hot, or very cold (e.g. Antarctica)

Chaparral: Dense, spiny, evergreen shrubs, mild rainy winters; long, hot, dry summers. Periodic fires, some plants require fire for seeds to germinate.

Temperate Grassland: Marked by seasonal drought and fires, and grazing by large animals. Rich habitat for agriculture, very little prairie exists in US today.

Temperate Deciduous Forest: Mid-latitudes with moderate amounts of moisture, distinct vertical strata: trees, understory shrubs, herbaceous sub-stratum. Loss of leaves in cold, many animals hibernate or migrate then. Original forests lost from North America by logging and clearing.

Coniferous forest: Largest terrestial biome on earth, old growth forests rapidly disappearing, usually receives lots of moisture as rain or snow.

Tundra: Permafrost (Permanent frozen ground), bitter cold, high winds and thus no trees. Has 20% of land surface on earth.