Ecology, Ecosystems, and the Environment

Chapter 19

Great Idea:Ecosystems are interdependent communities of

living things that recycle matter while energy flows through.

Ecology and Ecosystems

• Ecology– Natural living systems

• Ecosystems– Biotic and abiotic components

• Community– Producers, consumers, decomposers

Characteristics of Ecosystems

• Every ecosystem consists of both living and nonliving parts

• Energy flows through ecosystems• Matter is recycled by ecosystems

Characteristics of Ecosystems – cont.

• Every organism occupies an ecological niche

• Stable ecosystems achieve a balance among their populations

• Ecosystems are not permanent, but change over time

Energy Flows through Ecosystems

• Food Web– Interactions of organisms

• Trophic Levels– Photosynthetic organisms– Herbivores– Carnivores– Decomposers

• Most energy is lost as heat– 10% is transferred

Every Organism Occupies an Ecological Niche

• Ecological niche– Mode of survival

• Each plant/animal fills a niche– Organisms compete for dominance

Stable Ecosystems Achieve a Balance among Their Populations

• Homeostasis– Balance among populations

• Resources are limited– Some variation in populations– Overall relatively constant

The Law of Unintended Consequences

• It is virtually impossible to change one aspect of a complex system without affecting other parts of the systems, often in as-yet unpredictable ways.

Threats to the Global Ecosystem and Environment

The Problem of Urban Landfills

• Solid Waste– Nothing is ever thrown away

• Landfills– Decay slowed enormously

• Response – Recycling– Large depositories

Acid Rain and Urban Air Pollution

• Burning introduces chemicals– Nitrogen oxides, sulfur compounds,

hydrocarbons• Effects

– Air pollution• Production of bad ozone

– Acid rain• Reduction

– Reduce emissions• Power plants• Vehicles

Acid Rain

Acid Rain Destruction

The Ozone Problem

• Ozone– Molecule of 3 oxygen atoms– Absorbs ultraviolet radiation

• The ozone layer– Detection

• Aircraft sampling• Measure spectral lines from molecule

– Stratosphere• Highest concentration

The Ozone Layer

Lower Ozone over Antarctica

The Greenhouse Effect

• Greenhouse effect– Traps heat on earth

• Global warming– Climate change

• 3 main points– CO2 is a greenhouse gas– Burning fossil fuels increases CO2

– Average global temperature has significantly increased• 1990s warmest decade

The Greenhouse Effect

Carbon DioxideProduction Trend

Debates about Global Climate Change

• Increased CO2 levels– Responsible for temperature increase?

• World’s oceans– CO2 exchange with atmosphere

– Current circulation

• Solar energy output– Varies over time

Evolution

Chapter 25

Great Idea:All life on Earth evolved from single-celled

organisms by the process of natural selection.

The Fact of Evolution

• Evolution– Ongoing process of change

• Scientists accept evolution as fact– Debate various theories of HOW it

occurs, but no credible scientist denies that fact that it does occur.

The Fossil Record

• Fossils– Organism’s hard parts preserved

• Turned to rock• Replaced by minerals

• Fossil record– Fossils found, catalogued, and analyzed– Shows transitions– Incomplete

The Fossil Record – cont.

• Three key ideas– Older fossils more different– Increasing complexity with time– Most species have gone extinct (99%)

The Biochemical Evidence

• DNA– Evidence for evolution

– Changes slowly

– Also compare amino acid sequences• Cytochrome c

– Humans and chimps identical

– Rattlesnake 86% overlap

Evidence from Anatomy:Vestigial Organs

• Vestigial organs– Internal features– No useful function

• Examples– Appendix: humans– Wings: penguins– Hind legs: whales

Chemical Evolution

Black Smokers

• Black Smokers– Deep-ocean floor– Vents of mineral rich hot water– Diverse ecosystem

• Most primitive bacteria

• Hydrothermal zones– Site of life’s origin?

• Protected• Ideal chemical environment

The Ongoing Process of Science

• Did life also originate on Mars?– Evidence from a meteorite

Natural Selection and the Development of Complex Life

Natural Selection

• Charles Darwin

• Natural Selection– Variation in populations

• Some variation heritable

– More individuals born than will survive

• Adaptation

• Artificial selection

Dog Breeds

Charles Darwin

The Story of Life

• First cell– Natural selection

• Mutations

• Mutations– Random– Most not beneficial

• Environment– Impacts evolution

The Story of Life – cont.

• Eukaryotes• Colonies• Hard shell

– Cambrian explosion

A Fossil Microbe

Major Steps in the Evolution of Life

Mass Extinctions and the Rate of Evolution

• Rate of extinction– 10%-20% extinct in 5-6 million years

• Mass extinctions– 30%-90% extinct

• Mechanisms– Asteroid

• Evolution – Gradualism– Punctuated equilibrium

Giant Crater near theYucatan Peninsula

The Evolution of Human Beings

Thinking More about Evolution

• Young-earth creationism

• Intelligent design