Chapter 4 Evolution and Biodiversity Chapter 6 Evolution

Chapter 4 Evolution and Biodiversity

Chapter 6 Evolution and Biodiversity What is biodiversity? *Biodiversity is the variety of earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life.

Components……… species diversity genetic diversity ecosystem diversity functional diversity

Importance of species diversity species richness – number of different species Ø species evenness- relative abundance of individuals within each of those species Ø species diversity varies with geographic location Ø species rich ecosystems are productive and sustainable Ø

Core Case Study Earth: The Just-Right, Adaptable Planet Ø 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. Figure 4 -1

Biological Change Ø This has led to the variety of species we find on the earth today. Ø If the earth was only 1 day old…… Figure 4 -2

How Do We Know Which Organisms Lived in the Past? Ø Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis. Figure 4 -4

NATURAL SELECTION, AND ADAPTATION Ø Biological change by natural selection involves the change in a population’s genetic makeup through successive generations. l l genetic variability Mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.

Natural Selection and Adaptation: Leaving More Offspring With Beneficial Traits Ø Three conditions are necessary for biological change: l Genetic variability, traits must be heritable, trait must lead to differential reproduction. Ø An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

Coevolution: A Biological Arms Race Ø Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other. l This often happens between predators and prey species.

Hybridization and Gene Swapping: other Ways to Exchange Genes Ø New species can arise through hybridization. l Occurs when individuals to two distinct species crossbreed to produce an fertile offspring. (fairly rare…) Ø Some species (mostly microorganisms) can exchange genes without sexual reproduction. l Horizontal gene transfer

Limits on Adaptation through Natural Selection Ø 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. l Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

Common Myths about Natural Selection Ø Evolution through natural selection is about the most descendants. l l Organisms do not develop certain traits because they need them. Mutations are random. There is no such thing as genetic perfection. It is always possible for a mutation to occur which will lead to better natural selection.

GEOLOGIC PROCESSES, CLIMATE CHANGE, CATASTROPHES, AND EVOLUTION Ø 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. l l The locations of continents and oceanic basins influence climate. The movement of continents have allowed species to move.

225 million years ago 65 million years ago 135 million years ago Present Fig. 4 -5, p. 88

Climate Change and Natural Selection Ø Changes in climate throughout the earth’s history have shifted where plants and animals can live. Figure 4 -6

Catastrophes and Natural Selection Ø 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.

ECOLOGICAL NICHES AND ADAPTATION Each species in an ecosystem has a specific role or way of life. Ø Ecological niche is the sum total of a species’ use of the biotic and abiotic resources in the environment. Ø l l 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 Ø Generalist species tolerate a wide range of conditions. Ø Specialist species can only tolerate a narrow range of conditions. Figure 4 -7

SPOTLIGHT Cockroaches: Nature’s Ultimate Survivors Ø 350 million years old Ø 3, 500 different species Ø Ultimate generalist l l l Can eat almost anything. Can live and breed almost anywhere. Can withstand massive radiation. Figure 4 -A

Specialized Feeding Niches Ø Resource partitioning reduces competition and allows sharing of limited resources. Figure 4 -8

Some General Types of Species. . . Ø Native species: species that normally live & thrive in a particular ecosystem. Ø Nonnative species, Exotic species, Alien species: other species that migrate into an ecosystem or are introduced into an ecosystem by humans.

Frogs Galore Ø From ABC News, Environmental Science in the Headlines, 2005 DVD.

Some general species continued. . . Ø Indicator species: species that serve as early warnings that a community or an ecosystem is being damaged.

Some general species continued. . . Ø Keystone Species: species that play roles affecting many other organisms in an ecosystem. * Dung beetle * Sea otters * Gopher tortoises * Bats

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

Geographic Isolation Ø …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4 -10

Extinction: Lights Out Ø Extinction occurs when the population cannot adapt to changing environmental conditions. ØThe golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4 -11

Cenozoic Era Period Millions of years ago Quaternary Today Tertiary 65 Mesozoic Cretaceous Jurassic 180 Triassic Species and families experiencing mass extinction Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct Extinction within the next 50– 100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. Bar width represents relative number of living species 250 Extinction 345 Extinction Permian Paleozoic Carboniferous Devonian 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: 50% of animal families, including many trilobites. Fig. 4 -12, p. 93

Effects of Humans on Biodiversity Ø The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4 -13

GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION Ø We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding. Ø We have used genetic engineering to transfer genes from one species to another. Figure 4 -15

Genetic Engineering: Genetically Modified Organisms (GMO) Ø GMOs use recombinant DNA l genes or portions of genes from different organisms. Figure 4 -14

Phase 2 Make Transgenic Cell E. Coli A. tumefaciens (agrobacterium) Foreign DNA Plant cell Host DNA Nucleus Transfer plasmid copies to a carrier agrobacterium Transfer plasmid to surface of microscopic metal particle Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell Use gene gun to inject DNA into plant cell Fig. 4 -14, p. 95

Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits Fig. 4 -14, p. 95

Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits Stepped Art Fig. 4 -14, p. 95

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

Cloned Pooch Ø From ABC News, Biology in the Headlines, 2005 DVD.

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

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