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 –CO 2 is a greenhouse gas –Burning fossil fuels increases CO 2 –Average global temperature has significantly increased 1990s warmest decade

The Greenhouse Effect

Carbon Dioxide Production Trend

Debates about Global Climate Change Increased CO 2 levels –Responsible for temperature increase? World’s oceans –CO 2 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 –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 –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 the Yucatan Peninsula

The Evolution of Human Beings

Thinking More about Evolution Young-earth creationism Intelligent design