Chapter 50Chapter 50

An Introduction to Ecology and the Biosphere

(cont’d)

RECALL:

• Concept 50.1: Ecology is the study of interactions between organisms and the environment

• Concept 50.2: Interactions between organisms and the environment limit the distribution of species

• Concept 50.3: Abiotic and biotic factors influence the structure and dynamics of aquatic biomes

ECOLOGY

subfields

Organismal Ecology

Population Ecology

Community Ecology

Ecosystem Ecology

Landscape Ecology

ECOLOGY

Environmental Issues

Rachel Carson

Silent Spring

Precautionary Principle

Dispersal & Distribution

Biogeography Biogeographic Realms

Natural Range

Expansions

Species Transplants

Abiotic Factors

Biotic Factors

Temperature

Water

Sunlight

Wind

Rocks & Soil

Species Interactions

Predation

Competition

TODAY:•Aquatic Biomes– Lakes

– Wetlands

– Streams

– Rivers

– Estuaries

– Intertidal biomes

– Oceanic pelagic biomes

– Coral reefs

– Marine benthic biomes

•Terrestrial Biomes– Tropical Forests

– Deserts

– Savanna

– Chaparrals

– Temperate Grasslands

– Coniferous Forest

– Temperate Broadleaf Forests

– Tundra

• Concept 50.3: Abiotic and biotic factors influence the structure and dynamics of aquatic biomes

• Varying combinations of both biotic and abiotic factors

– determine the nature of Earth’s many biomes

• Biomes

– are the major types of ecological associations that occupy broad geographic regions of land or water

Aquatic zones

• Many aquatic biomes

– are stratified into zones or layers defined by light penetration, temperature, and depth

Marine zonation. Like lakes, the marine environment is generally classified on the basis of light penetration (photic and aphotic zones), distance from shore and water depth (intertidal, neritic, and oceanic zones), and whether it is open water (pelagic zone) or bottom (benthic and abyssal zones).

Zonation in a lake. The lake environment is generally classified on the basis of three physical criteria: light penetration (photic and aphotic zones), distance from shore and water depth (littoral and limnetic zones), and whether it is open water (pelagic zone) or bottom (benthic zone).

(a)

Littoralzone Limnetic

zone

Photiczone

Benthiczone

Aphoticzone

Pelagiczone

Intertidal zone

Neritic zone Oceanic zone

0

200 mContinentalshelf

Photic zone

Pelagic zone

Aphoticzone

Benthiczone

2,500–6,000 m

Abyssal zone(deepest regions of ocean floor)

(b)

Figure 50.16a, b

Lakes•physical environment: standing body of water; can be stratified; seasonal thermocline

•chemical environment: oligotrophic = deep, nutrient-poor, oxygen rich; eutrophic lakes = shallower, increased nutrients, oxygen depleted in winter; mesotrophic = moderate amount of nutrients, phytoplankton productivity

•geologic features: oligotrophic lakes have less surface area compared to depth; oligotrophic lake can become eutrophic over time

•photosynthetic organisms: ps. rates higher in eutrophic lakes; plants in littoral zone; phytoplankton + cyanobacteria in limnetic zone

•animals: zooplankton in limnetic zone; invertebrates in benthic zone; fish present throughout if O2 present

•human impact: runoff from fertilizers, dumping of municipal waste = nutrient enrichment – algal blooms, O2 depletion

Figure 50.17

An oligotrophic lake in Grand Teton, Wyoming

A eutrophic lake in Okavango delta, Botswana

LAKES

Wetlands•physical environment: area covered with water for long enough period to support aquatic life

•chemical environment: high organic production, decomposition;low dissolved O2

•geologic features: basin wl.= shallow basin; riverine wl. = shallow, flooded banks of rivers, streams; fringe wl. = along coasts of lakes, seas depending on tides

•photosynthetic organisms: plants with adaptations to grow in water with low O2

•animals: invetebrates – birds; herbivores, carnivores

•human impact: draining & filling destroyed up to 90% of wl. in some regions

WETLANDS

Okefenokee National Wetland Reserve in Georgia

Streams and Rivers•physical environment: current; headwater streams = cold, clear, turbulent; downstream = warmer, more turbid; stratified

•chemical environment: salt, nutrient content increases from headwater to mouth; headwater O2 rich

•geologic features: headwater narrow, rocky bottom; downstream – wider, bottom silty

•photosynthetic organisms: streams through grassland or dessert are rich in algae or rooted plants; in forests leaves etc. from terrestrial plants primary food source for consumers

•animals: fishes, invertebrates

•human impact: municipal, agricultural, industrial pollution, damming

STREAMS AND RIVERS

A headwater stream in theGreat Smoky Mountains

The Mississippi River farform its headwaters

Estuaries•physical environment: transition area between river & sea; complex flow patterns; higher density sea water bottom of estuary channel

•chemical composition: salinity variable; nutrient from river make estuaries very productive

•geologic features: tidal channels, islands, levees, mudflats

•photosynthetic organisms: grasses, algae including phytoplankton

•animals: invertebrates, fishes; important breeding grounds for marine species; feeding area for waterfowl

•human impact: pollution from upstream, filling, dredging

An estuary in a low coastal plain of Georgia

ESTUARIES

Intertidal Zones•physical environment: periodically submerged & exposed by tides; upper zones greater exposure to air, more variation in environment (temp., salinity, wave action)

•chemical environment: O2, nutrient levels high

•geologic features: rocky or sandy substrate; variable influence of tides depending on coastline

•photosynthetic organisms: attached marine algae

•animals: invertebrates with special adaptations to attach to substrate

•human impact: oil pollution, recreational use

INTERTIDAL ZONES

Rocky intertidal zone on the Oregon coast

Ocean pelagic biome•physical environment: open water, mixed by ocean currents; higher clarity that coastal zones, photic zone is deeper

•chemical environment: O2 high; nutrient levels low; temperate regions there is surface turn over

•geologic features: vast, deep waters; 70% of Earth’s surface

•photosynthetic organisms: phytoplankton

•animals: zooplankton, free swimming invertebrates, vertebrates

•human impact: overfishing, pollution (oil spills, waste dumping)

Open ocean off the island of Hawaii

OCEANIC PELAGIC BIOME

Coral reefs•physical environment: limited to photic zones of stable tropical environments with high water clarity

•chemical environment: high O2, stable salinity, stable nutrient levels

•geologic features: coral reef formed from calcium carbonate of corals; needs solid substrate

•photosynthetic organisms: dinoflagellate algae within tissues of corals; red, green marine algae

•animals: cnidarians predominant animals; fish, invertebrates

•human impact: poisons, explosives for aquarium trade, global warming, pollution

A coral reef in the Red Sea

CORAL REEFS

Marine benthic •physical environment: seafloor below neritic zone (WATER THAT IS ABOVE THE CONTINETIAL SHELF & pelagic zone; no sunlight in benthos beneath pelagic; deep benthic = abyssal zone (cold 3ºC, high pressure)

•chemical environment: O2 sufficient for diversity of animals

•geologic features: soft sediments; some rocky substrate; submarine mountains; volcanoes

•food producing organisms: ps organisms only in shallow benthos; some organisms associated with deep-sea hydrothermal vents- chemoautotrophic prokaryotes

•animals: neritic benthic – invertebrates, fishes; deep water tube worms; arthropods, echinoderms

•human impact: overfishing, dumping

A deep-sea hydrothermal vent community

MARINE BENTHIC ZONE

• Concept 50.4: Climate largely determines the distribution and structure of terrestrial biomes

• Climate

– is particularly important in determining why particular terrestrial biomes are found in certain areas

Climate and Terrestrial Biomes

• Climate has a great impact on the distribution of organisms, as seen on a climograph

Figure 50.18

Desert Temperate grassland Tropical forest

Temperatebroadleafforest

Coniferousforest

Arctic andalpinetundra

Annual mean precipitation (cm)

Ann

ual m

ean

tem

pera

ture

(ºC

)

100 200 300 400

30

15

0

15

The distribution of major terrestrial biomes

30N

Tropic ofCancer

Equator

Tropic ofCapricorn

30S

Key

Tropical forest

Savanna

Desert

Chaparral

Temperate grassland

Temperate broadleaf forest

Coniferous forest

Tundra

High mountains

Polar ice

Figure 50.19

General Features of Terrestrial Biomes

• Terrestrial biomes

– are often named for major physical or climatic factors and for their predominant vegetation

• Stratification

– is an important feature of terrestrial biomes

Tropical forest•distribution: equatorial, subequatorial

•precipitation: tropical rain forests -relatively constant, 200-400 cm annually; tropical dry forests – 150-200 cm annually (6-7 month dry season)

•temperature: 25-29ºC

•plants: stratified – canopy, subcanopy trees; rain forest -broadleaf evergreen dominant; deciduous broadleaf in tropical dry forest

•animals: most animal diversity than any other terrestrial biome

•human impact: destruction for agriculture, development

TROPICAL FOREST

A tropical rain forest in Borneo

Desert•distribution: in band near 30º N & S latitude or interior of continents

•precipitation: low, highly variable; less than 30 cm per year

•temperature: variable; can exceed 50ºC; some cold deserts -30ºC

•plants: low, scattered vegetation; high proportion of bare ground; succulents, shrubs

•animals: reptiles, rodents, insects; many species nocturnal; adaptations to deal with scarce water

•human impact: conversion to irrigated land, urbanization

DESERT

The Sonoran Desert in southern Arizona

Savanna•distribution: equatorial, subequatorial

•precipitation: 30-50 cm per year; dry season 8-9 months

•temperature: 24-29ºC

•plants: scattered trees; adapted for seasonal drought; grasses + forbs dominant

•animals: large herbivores; insects

•human impact: cattle ranching, overhunting

SAVANNA

A typical savanna in Kenya

Chaparral•distribution: midlatitude coastal regions

•precipitation: rainy winters, dry summers; 30-50 cm annual

•temperature: fall, winter, spring 10-12ºC; summer 30-40ºC

•plants: shrubs, small trees; high plant diversity; adaptations to drought

•animals: browsing herbivores, high diversity of small animals (amphibians, birds, reptiles)

•human impact: agriculture,urbanization

CHAPARRAL

An area of chaparral in California

Temperate grasslands•distribution: throughout various regions

•precipitation: dry winters, wet summers; 30-100 cm

•temperature: cold winters -10ºC; hot summers 30ºC

•plants: grasses & forbs; adapted to drought, fire

•animals: large grazers, burrowing animals

•human impact: agriculture

Sheyenne National Grassland in North Dakota

TEMPERATE GRASSLAND

Coniferous forest•distribution: broad band across northern N America & Erasia to edge of arctic tundra

•precipitation: 30-70 cm, periodic droughts; coastal coniferous forests 300 cm

•temperature: winters cold, long; summers may be hot

•plants: cone-bearing trees

•animals: large herbivores, carnivores

•human impact: logging

Rocky Mountain National Park in Colorado

CONIFEROUS FOREST

Temperate broadleaf forest•distribution: midlatitude in northern hemisphere

•precipitation: 70-200 cm annually

•temperature: winter 0ºC; summers 30ºC

•plants: high diversity; deciduous trees dominant

•animals: mammals, birds, insects

•human impacts: logging, agriculture, urban developement

Figure 50.20

TEMPERATE BROADLEAF FOREST

Great Smoky Mountains National Park in North Carolina

Tundra•distribution: arctic (20% of surface)

•precipitation: 20-60 cm; some areas 100 cm

•temperature: winters long, cold -30ºC; summers short cool 10ºC

•plants: herbaceous (lichens, mosses, grasses, forbs, dwarf trees); permafrost prevents water infiltration into soil

•animals: large grazing herbivores, large carnivores, migratory birds

•human impact: mineral, oil extraction

TUNDRA

Denali National Park, Alaska, in autumn

Take home questions:Which of the following statements best describes the

effect of climate on biome distribution?

A) Knowledge of annual temperature and precipitation is sufficient to predict which biome will be found in an area.

B) Fluctuation of environmental variables is not important if areas have the same annual temperature and precipitation means.

C) It is not only the average climate that is important in determining biome distribution, but also the pattern of climatic variation. On final Test.

D) Temperate forests, coniferous forests, and grasslands all have the same mean annual temperatures and precipitation.

E) Correlation of climate with biome distribution is sufficient to determine the cause of biome patterns.

Imagine some cosmic catastrophe that jolts Earth so that it is no longer tilted. Instead, its axis is perpendicular to the line between the Sun and Earth. The most predictable effect of this change would be:

A) No more night and day.

B) A big change in the length of the year.

C) A cooling of the equator.

D) A loss of seasonal variations at northern and southern latitudes. In the textbook.

E) The elimination of ocean currents.

Which of the following events might you predict to occur if the tilt of Earth's axis relative to its plane of orbit was increased beyond 23.5 degrees?

A) Summers in the United States might become warmer.

B) Winters in Australia might become more severe.

C) Seasonal variation at the equator might decrease.

D) Both A and B are correct.

E) A, B, and C are all correct.

If a meteor impact or volcanic eruption injected a lot of dust into the atmosphere and reduced sunlight reaching Earth's surface by 70% for one year, all of the following marine communities would be greatly affected except a

A) deep-sea vent community.

B) coral reef community.

C) benthic community.

D) pelagic community.

E) estuary community.