Evolution and Biodiversity

Biological EvolutionHas led to the variety of species we find on Earth today

How Do We Know Which Organisms Lived in the Past?

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

Natural Selection• 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 by natural selection

Genetic variability, traits must be heritable, trait must lead to differential reproduction

Zebra mussels on native mussel

AdaptationAn adaptive trait is any heritable trait that enables an

organism to survive through natural selection and reproduce better under prevailing environmental conditions

Flying fish

Sun fish

Loach

Fish Adaptations

Tri-pod fish

Coevolution: A Biological Arms Race

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

The Japanese hornet feeds on Japanese honeybees

Japanese honeybees defend their nests and their young by

surrounding the Japanese hornet and fluttering their wings

increasing the body temperature of the hornet and exposing the

hornet to increased carbon dioxide levels

Limits on Adaptation through Natural Selection

• 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.

Gestation period is 22 months for an elephant

Common Myths about Evolution through Natural Selection

• 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.

GEOLOGIC PROCESSES, CLIMATE CHANGE, CATASTROPHES, AND EVOLUTION

• 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.

Fig. 4-5, p. 88

135 million years ago

Present65 million years ago

225 million years ago

Climate Change and Natural Selection

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

Figure 4-6Figure 4-6

Catastrophes and Natural Selection• 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.

Meteor Crater, Arizona

SPECIATION, EXTINCTION, AND BIODIVERSITY

• 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.

Geographic Isolation

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

Figure 4-10Figure 4-10

ECOLOGICAL NICHES AND ADAPTATION

• 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.

Specialized Feeding Niches

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

Figure 4-8Figure 4-8

Fig. 4-8, pp. 90-91

Piping plover feedson insects and tinycrustaceans on sandy beaches

(Birds not drawn to scale)

Black skimmerseizes small fishat water surface

Flamingofeeds on minuteorganismsin mud

Scaup and otherdiving ducks feed on mollusks, crustaceans,and aquatic vegetation

Brown pelican dives for fish,which it locates from the air

Avocet sweeps bill throughmud and surface water in search of small crustaceans,insects, and seeds

Louisiana heron wades intowater to seize small fish

Oystercatcher feeds onclams, mussels, and other shellfish into which it pries its narrow beak

Dowitcher probes deeplyinto mud in search ofsnails, marine worms,and small crustaceans

Knot (a sandpiper)picks up worms andsmall crustaceans leftby receding tide

Herring gull is atireless scavenger

Ruddy turnstone searches

under shells and pebbles

for small invertebrates

Evolutionary Divergence

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

Figure 4-9Figure 4-9

Ecological Roles

Generalist species

• Broad niche• Live in many different areas• Eat variety of foods• Tolerate wide range

environmental conditions

Specialist species

• Narrow niche• May only live in one type of

habitat• Few types of food• Tolerate narrow range of

environmental conditions

Extinction: Lights Out

• 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.Figure 4-11Figure 4-11

SPOTLIGHTCockroaches: Nature’s Ultimate

Survivors• 350 million years old• 3,500 different species• Ultimate generalist

– Can eat almost anything.– Can live and breed almost

anywhere.– Can withstand massive

radiation.

Figure 4-AFigure 4-A

Fig. 4-12, p. 93

Tertiary

Bar width represents relative number of living speciesEra Period

Species and families experiencing

mass extinction

Millions ofyears ago

Ordovician: 50% of animal families, including many trilobites.

Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

500

345

Cambrian

Ordovician

Silurian

Devonian

Extinction

Extinction

Pal

eozo

icM

eso

zoic

Cen

ozo

ic

Triassic: 35% of animal families, including many reptiles and marine mollusks.

Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.Carboniferous

Permian

Current extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including manyforaminiferans and mollusks.

Extinction

Extinction

Triassic

Jurassic

Cretaceous

250

180

65Extinction

ExtinctionQuaternary Today

GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION

• We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding.

We have used We have used genetic engineeringgenetic engineering to transfer genes to transfer genes from one species to from one species to another.another.

Figure 4-15Figure 4-15

Using biotechnology to develop blight-resistant American Chestnut

Before 1900 the American Chestnut made up 25% of the standing trees in the Appalachian forest

These trees grew to 100 ft rapidly and their trunks were more than 6 ft in diameter

The chestnut blight was introduced into the U.S. and now the tree rarely reaches 30 ft before dying

Scientists have created transgenic American Chestnut resistant to the chestnut blight

Transgenic trout with six-pack abs = more

muscle mass which is more profit

Transgenic fish which glow were originally developed to detect pollution – but developers can

make more money in the aquarium trade

Controversy Over Genetic Engineering

• 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?

Case Study: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).

The End