Evolution and Biodiversity

Has led to the variety of species we find on Earth today Biological Evolution Has 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.

Zebra mussels on native mussel 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

Adaptation An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions

Flying fish Loach Fish Adaptations Sun fish 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.

225 million years ago 225 million years ago 135 million years ago Figure 4.5 Geological processes and biological evolution. Over millions of years the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species as land areas split apart and promote the rise of new species when once isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s huge plates separated and eventually resulted in today’s locations of the continents (bottom right). 65 million years ago Present Fig. 4-5, p. 88

Climate Change and Natural Selection Changes in climate throughout the earth’s history have shifted where plants and animals can live. Figure 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 4-10

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 4-8

Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Ruddy turnstone searches under shells and pebbles for small invertebrates Herring gull is a tireless scavenger Brown pelican dives for fish, which it locates from the air Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Black skimmer seizes small fish at water surface Louisiana heron wades into water to seize small fish Figure 4.8 Natural capital: specialized feeding niches of various bird species in a coastal wetland. Such resource partitioning reduces competition and allows sharing of limited resources. Piping plover feeds on insects and tiny crustaceans on sandy beaches Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation Knot (a sandpiper) picks up worms and small crustaceans left by receding tide (Birds not drawn to scale) Fig. 4-8, pp. 90-91

Evolutionary Divergence Each species has a beak specialized to take advantage of certain types of food resource. Figure 4-9

Ecological Roles Generalist species Specialist species Broad niche Live in many different areas Eat variety of foods Tolerate wide range environmental conditions 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 4-11

SPOTLIGHT Cockroaches: 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-A

Species and families experiencing mass extinction Bar width represents relative number of living species Millions of years ago Era Period Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Quaternary Today Cenozoic Tertiary Extinction 65 Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Mesozoic Jurassic Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. 180 Triassic Extinction Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. 250 Permian Carboniferous Extinction 345 Figure 4.12 Fossils and radioactive dating indicate that five major mass extinctions (indicated by arrows) have taken place over the past 500 million years. Mass extinctions leave many organism roles (niches) unoccupied and create new niches. Each mass extinction has been followed by periods of recovery (represented by the wedge shapes) called adaptive radiations. During these periods, which last 10 million years or longer, new species evolve to fill new or vacated niches. Many scientists say that we are now in the midst of a sixth mass extinction, caused primarily by human activities. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Devonian Paleozoic Silurian Ordovician Extinction 500 Ordovician: 50% of animal families, including many trilobites. Cambrian Fig. 4-12, p. 93

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 genetic engineering to transfer genes from one species to another. Figure 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

six-pack abs = more muscle mass which is more profit 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