 How do scientists account for the development of life on earth?
 What is biological evolution by natural selection, and how can it account for the current diversity of organisms on the earth?
 How can geologic processes, climate change and catastrophes affect biological evolution?
 What is an ecological niche, and how does it help a population adapt to changing the environmental conditions?

 How do extinction of species and formation of new species affect biodiversity?
 What is the future of evolution, and what role should humans play in this future?
 How did we become such a powerful species in a short time?

The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.
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InfoTrac: Life After Earth: Imagining Survival Beyond This Terra Firma.
Richard Morgan. The New York Times , August 1, 2006 pF2(L).
InfoTrac: Rhinos Clinging to Survival in the Heart of Borneo, Despite
Poaching. US Newswire , March 17, 2006.
InfoTrac: Newfound Island Graveyard May Yield Clues to Dodo Life of
Long Ago. Carl Zimmer. The New York Times , July 4, 2006 pF3(L).
NASA: Evolvable Systems
American Museum of Natural History: Tree of Life
PBS: Evolution

 This video clip is available in CNN Today
Videos for Environmental Science, 2004,
Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

 During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20 o C.

 1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change.

Chemical Evolution
(1 billion years)
Biological Evolution
(3.7 billion years)
Formation of the earth’s early crust and atmosphere
Small organic molecules form in the seas
Large organic molecules
(biopolymers) form in the seas
First protocells form in the seas
Single-cell prokaryotes form in the seas
Single-cell eukaryotes form in the seas
Variety of multicellular organisms form, first in the seas and later on land

 This has led to the variety of species we find on the earth today.
Figure 4-2

Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight
Age of reptiles
Age of mammals
Insects and amphibians invade the land
Recorded human history begins about 1/4 second before midnight
Origin of life
(3.6-3.8 billion years ago)
First fossil record of animals
Plants begin invading land Evolution and expansion of life

 Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.

 Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations.
 genetic variability

Mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.

 Three conditions are necessary for biological evolution:

Genetic variability, traits must be heritable, trait must lead to differential reproduction .
 An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

 Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other.

This often happens between predators and prey species.

 New species can arise through hybridization.

Occurs when individuals to two distinct species crossbreed to produce an fertile offspring.
 Some species (mostly microorganisms) can exchange genes without sexual reproduction.

Horizontal gene transfer

 A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce.

Humans have a relatively slow generation time
(decades) and output (# of young) versus some other species.

 Evolution through natural selection is about the most descendants.

Organisms do not develop certain traits because they need them.

There is no such thing as genetic perfection.

 The movement of solid (tectonic) plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones.

The locations of continents and oceanic basins influence climate.

The movement of continents have allowed species to move.

225 million years ago
135 million years ago
65 million years ago
Present

 Changes in climate throughout the earth’s history have shifted where plants and animals can live.

18,000 years before present
Northern Hemisphere
Ice coverage
Legend
Continental ice
Sea ice
Land above sea level
Modern day
(August)
Note:
Modern sea ice coverage represents summer months

 Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

 Each species in an ecosystem has a specific role or way of life.

Fundamental niche : the full potential range of physical, chemical, and biological conditions and resources a species could theoretically use.

Realized niche : to survive and avoid competition, a species usually occupies only part of its fundamental niche.

Generalist and Specialist Species:
Broad and Narrow Niches
 Generalist species tolerate a wide range of conditions.
 Specialist species can only tolerate a narrow range of conditions.

Specialist species with a narrow niche
Niche separation
Generalist species with a broad niche
Niche breadth
Region of niche overlap
Resource use

 350 million years old
 3,500 different species
 Ultimate generalist



Can eat almost anything.
Can live and breed almost anywhere.
Can withstand massive radiation.

 Resource partitioning reduces competition and allows sharing of limited resources.

Black skimmer seizes small fish at water surface
Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds
Brown pelican dives for fish, which it locates from the air
Herring gull is a tireless scavenger
Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans
Ruddy turnstone searches under shells and pebbles for small invertebrates
Flamingo feeds on minute organisms in mud
Louisiana heron wades into water to seize small fish
Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation
Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak
Piping plover feeds on insects and tiny crustaceans on sandy beaches
Knot (a sandpiper) picks up worms and small crustaceans left by receding tide
(Birds not drawn to scale)

 Each species has a beak specialized to take advantage of certain types of food resource.

Fruit and seed eaters
Greater Koa-finch
Insect and nectar eaters
Kuai Akialaoa
Amakihi
Kona Grosbeak
Crested Honeycreeper
Akiapolaau
Maui Parrotbill Apapane
Unknown finch ancestor

 Speciation: A new species can arise when member of a population become isolated for a long period of time.

Genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited.

 …can lead to reproductive isolation, divergence of gene pools and speciation.

Early fox
Population
Spreads northward and southward and separates
Northern population
Southern
Population
Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage.
Arctic Fox
Different environmental conditions lead to different selective pressures and evolution into two different species.
Gray Fox
Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat.

 Extinction occurs when the population cannot adapt to changing environmental conditions.
 The golden toad of Costa Rica’s
Monteverde cloud forest has become extinct because of changes in climate.

Era Period
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Millions of years ago
Today
65
180
250
345
Bar width represents relative number of living species
Extinction
Extinction
Extinction
Species and families experiencing mass extinction
Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50 –100 years.
Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks.
Triassic: 35% of animal families, including many reptiles and marine mollusks.
Extinction
Extinction
Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.
Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.
Silurian
Ordovician
Cambrian
500
Extinction
Ordovician: trilobites.
50% of animal families, including many

 The scientific consensus is that human activities are decreasing the earth’s biodiversity.

Millions of years ago
Terrestrial organisms
Marine organisms

 We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding .
 We have used genetic engineering to transfer genes from one species to another.

Genetically Modified Organisms (GMO)
 GMOs use recombinant
DNA
 genes or portions of genes from different organisms.

Phase 1
Make Modified Gene E. coli
Cell
Extract DNA
Extract
Plasmid
Genetically modified plasmid
Gene of interest
DNA
Plasmid
Identify and extract gene with desired trait
Identify and remove portion of DNA with desired trait
Remove plasmid from DNA of
Insert extracted
(step 2) into plasmid
(step 3)
E. coli
Insert modified plasmid into E. coli
Grow in tissue culture to make copies

Phase 2
Make Transgenic Cell
E. Coli A. tumefaciens
(agrobacterium)
Foreign DNA
Plant cell
Host DNA
Transfer plasmid copies to a carrier agrobacterium
Nucleus
Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell
Transfer plasmid to surface of microscopic metal particle
Use gene gun to inject
DNA into plant cell

Phase 3
Grow Genetically Engineered Plant
Transgenic cell from Phase 2
Cell division of transgenic cells
Culture cells to form plantlets
Transgenic plants with new traits
Transfer to soil

Phase 3
Grow Genetically
Engineered Plant
Transgenic cell from Phase 2
Cell division of transgenic cells
Culture cells to form plantlets
Transgenic plants with new traits
Transfer to soil
Stepped Art

To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
 Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available?
 a. No. Human cloning will lead to widespread human rights abuses and further overpopulation.
 b. Yes. People would benefit with longer and healthier lives.

 Biologists are learning to rebuild organisms from their cell components and to clone organisms.

Cloning has lead to high miscarriage rates, rapid aging, organ defects.
 Genetic engineering can help improve human condition, but results are not always predictable.

Do not know where the new gene will be located in the DNA molecule’s structure and how that will affect the organism.

 There are a number of privacy, ethical, legal and environmental issues.
 Should genetic engineering and development be regulated?
 What are the long-term environmental consequences?

How Did We Become Such a Powerful
Species so Quickly?
 We lack:


 strength, speed, agility.
weapons (claws, fangs), protection (shell).
poor hearing and vision.
 We have thrived as a species because of our:
 opposable thumbs, ability to walk upright, complex brains (problem solving).