Transcript Figure 50.1 (p. 1093) – Distribution and abundance of the red

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) – Predatorremoval 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 50.12 (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 50.15 (p. 1104) – Lake stratification and seasonal
turnover.
III. Aquatic and terrestrial biomes (Biome = major ecosystem
type)  Read and know pages 1106-1117 (ed. 6) or pages
1092-1103 (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 50.17 (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 50.24 (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.