Chapter 52: Introduction to Ecology and the Biosphere

Ecology• oikos - home!

• logos - to study!

• Ecology - the study of interactions between organisms and the environment !

• Answer important questions:!

• Where do organisms live?!

• Why do organisms live where they live?!

• What factors determine how many organisms live in one place?

Climate• Climate - long-term prevailing weather

conditions in a particular area!

• Major components: temperature, precipitation, sunlight, and wind!

• Macroclimate - patterns on global, regional, and landscape level!

• Microclimate - defined by fine-scale differences in the environment that affect light and wind patterns

Global Climate• Determined by input of

solar energy!

• Sun’s warming of the atmosphere, land, and water that causes temperature variations, cycles of air movements, and evaporation of water all determine latitudinal variations in climate

Latitudinal variation in sunlight intensity

90°N (North Pole) 60°N

30°N 23.5°N (Tropic of Cancer

60°S 90°S (South Pole)

0° (Equator)

23.5°S (Tropic of Capricorn) 30°S

Low angle of incoming sunlight

Atmosphere

Sun overhead at equinoxes

Low angle of incoming sunlight

Fig. 52.3

Global Air Circulation• Water evaporates in the tropics, and warm, wet air masses flow from the tropics

toward the poles!

• Rising air masses release water !

• Dry, descending air masses create arid climates (30 degrees north and south of the equator)!

• Trade winds blow east to west in the tropics and westerlies blow from west to east in the temperate zones

Global air circulation and precipitation patterns

Westerlies

Northeast trades

Southeast trades

Westerlies

30°N

0°

ARID ZONE

66.5°N (Arctic Circle)

30°N

0°

30°S

60°N

60°S

66.5°S (Antarctic Circle)

Descending dry air absorbs moisture.

Ascending moist air releases moisture.

Fig. 52.3b

Seasonality• Variations of light and temperature increase steadily

toward the poles!

• Impacted by tilt of the Earth at high latitudesMarch equinox

December solstice

September equinox

60°N

30°S

30°N

0° (equator)

Constant tilt of 23.5° June solstice

Fig. 52.4

Regional, Local, and Seasonal Effects

• Bodies of water!

• Ocean currents (ex. Gulf Stream)!

• Coastal zones (climate moderation)

Cooler

air sinks

over water.

3

Air cools at

high elevation. 2 1 Warm air

over land rises.

4 Cool air over water

moves inland, replacing

rising warm air over land.

Indian Ocean

Subtropical Gyre

California Current 30°N North Pacific

Subtropical Gyre

30°S

Equator

South Pacific Subtropical Gyre

Labrador Current

Gulf Stream North Atlantic Subtropical

Gyre

South Atlantic

Subtropical Gyre

Antarctic Circumpolar Current Fig. 52.5

Regional, Local, and Seasonal Effects

• Mountains!

• Effect amount of sunlight reaching an area!

• Effect rainfall!

• Temperature !

• Rain shadow

Air flow

Ocean

Mountain range

Leeward side of mountains

Fig. 52.6

Global Climate Change• Greatly impact the

biosphere!

• May be able to predict impact by studying previous changes (ex. glaciers retreating)!

• Species that have difficulty dispersing may have smaller ranges or become extinct

Current range Predicted range Overlap

(a) 4.5°C warming over next century

(b) 6.5°C warming over next century

Fig. 52.7

Sweden

Finland

Expanded range in 1997 Range in 1970 Fig. 52.8

Biomes

• Major types of ecological associations that occupy broad geographic regions in land and water!

• Climate is key to determination!

• Characterized by vegetation type (terrestrial biomes) and physical environment (aquatic biomes)

Climographs• Plot

temperature and precipitation in a region!

• Biomes are affected by the pattern of temperature and precipitation (not just the averages)

Temperate broadleaf forest

Arctic and alpine tundra

Northern coniferous forest

Ann

ual m

ean

tem

pera

ture

(°C

)

Temperate grassland Tropical forest

30

15

0

-15

Desert

Annual mean precipitation (cm) 0 400 100 200 300

Figure 52.10

General Features of Terrestrial Biomes

• Usually grade into each other (no sharp boundaries)!

• Ecotone - area of integration between biomes (may be wide or narrow)!

• Vertical layering !

• Provides diverse habitats!

• Convergent Evolution!

• Can arise in distant biomesCereus peruvianus

Euphorbia canariensis

Fig. 52.11

Disturbance and Terrestrial Biomes

• Disturbance - event such as a storm, fire, or human activity that changes a community!

• Fire suppression

Aquatic Biomes• Largest part of the biosphere by area!

• Freshwater vs. Marine!

• Oceans !

• 75% of earth’s surface!

• Evaporation of oceans provides most of the planet’s rainfall!

• Temperature has major impact on climate and wind patterns!

• Algae and photosynthetic bacteria supply a substantial portion of the world’s oxygen and consume carbon dioxide!

• Freshwater - linked to soils and biotic components of the surrounding terrestrial biome

Zonation in Aquatic Biomes• Many are stratified into zones or

layers defined by light penetration, temperature, and depth!

• Pelagic zone: made of the photic zone and aphotic zone!

• Deep aphotic zone is the the abyssal zone (2,000 to 6,000m)!

• Benthic zone: organic and inorganic sediment at the bottom!

• Detritus - dead organic matter that falls from the productive surface

(a) Zonation in a lake

Littoral zone Limnetic

zone

Photic zone

Benthic zone Aphotic

zone

Pelagic zone

(b) Marine zonation

0 200 m

Continental shelf

2,000- 6,000 m

Abyssal zone

Benthic zone

Photic zone

Intertidal zone Neritic zone Oceanic zone

Aphotic zone

Pelagic zone

Fig. 52.13

Thermocline• In oceans and most lakes this temperature boundary separates

warm upper layer from cold deeper water!

• Many lakes undergo semiannual mixing of the waters (turnover)!

• Turnover mixes oxygenated water from the surface with nutrient-rich water from the bottom

Winter Spring

Thermocline

Autumn

0° 2°

4°C 4°C

4°

4°C

4°

4°C

22° 18°

8°

Summer

Fig. 52.14

Lakes• Great size variation!

• Oligotrophic lakes - nutrient poor and oxygen-rich!

• Eutrophic lakes - nutrient rich and oxygen poor!

• Littoral zone - shallow, well-lighted, close to shore!

• Limnetic zone - deep water, small drifting animals (zooplankton) that graze on phytoplankton

An oligotrophic lake in Grand Teton National Park, Wyoming

A eutrophic lake in the Okavango Delta, Botswana

Fig. 52.16

Distribution of Species• Result of

ecological and evolutionary relationships through time!

• Events in ecological time can lead to evolution

Kangaroos/km2

> 20

10–20

5–10

1–5

0.1–1

< 0.1 Limits of

distribution

Climate in northern Australia

is hot and wet, with seasonal

drought.

Red kangaroos

occur in most

semiarid and arid

regions of the

interior, where

precipitation is

relatively low and

variable from

year to year.

Southeastern Australia

has a wet, cool climate. Southern Australia has

cool, moist winters and

warm, dry summers. Tasmania

• Red Kangaroo!

• Abiotic factors!

• Biotic Factors

Factors Limiting DistributionWhy is species

X absent from an area?

Does dispersal limit its

distribution? No

Yes

Yes

Yes

No

No

Does behavior limit its

distribution? Do biotic factors (other species)

limit its distribution?

Do abiotic factors limit its distribution?

Habitat selection

Area inaccessible or insufficient time Predation,

parasitism, competition, disease

Water Oxygen Salinity pH Soil nutrients, etc.

Physical factors

Chemical factors

Temperature Light Soil structure Fire Moisture, etc.

Fig. 52.18

Dispersal and Distribution

• Dispersal - movement of individuals away from centers of high population density or from area of origin

New areas

occupied Year

1996

1989

1974

Natural Range Expansion and Adaptive Radiation

• Natural range expansions show influence of dispersal on distribution (ex. cattle egrets) !

• Adaptive radiation happens in rare cases of long-distance dispersal (ex. Hawaiian silverswords)

Current

1970

1970 1966 1965 1960

1961 1958

1943

1951 1937

1956

Fig. 52.19

Species Transplants

• Organisms intentionally or accidentally relocated from their original distribution !

• If successful, it indicates that the species potential range is larger than current range.

Biotic Factors

• Impact distribution!

• Predation, herbivory, competition

Both limpets and urchins removed

Only urchins removed

RESULTS

Seaw

eed

cove

r (%

)

Only limpets removed Control (both urchins and limpets present)

Sea urchin

Limpet

100

80

60

40

20

0 February

1983 August

1983 August

1982 February

1984

Fig. 52.20

Abiotic Factors

• Also impact distribution !

• Temperature, water, sunlight, salinity, wind, rock and soil

Fig 52.21