evolution and biodiversity. biological evolution has led to the variety of species we find on earth...
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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