Evolution and Biodiversity Overview Questions How do scientists

Evolution and Biodiversity

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

Overview Questions (cont’d) Ø How do extinction of species and formation of new species affect biodiversity? Ø What is the future of evolution, and what role should humans play in this future? Ø How did we become such a powerful species in a short time?

Rest assured, you are not alone!

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

In the Beginning…according to Science l Chemical Evolution- (hypothesis) the first organic (life forming) molecules formed from inorganic molecules and energy; formed protocells l Lightening; Heat (geothermal); Radiation (UV-sun) l. Produced by Stanley Miller and Harold Urey l Biological Evolution-the change in a populations’ genetic make-up through successive generations (takes time; not on an individual basis) l Evidence from fossils (comparative anatomy) and DNA

ORIGINS OF LIFE Ø 1 billion years of chemical change to form the first cells, followed by about 3. 7 billion years of biological change. Figure 4 -2

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

Modern humans (Homo sapiens) appear about 2 seconds before midnight Age of mammals Age of reptiles Insects and amphibians invade the land Recorded human history begins about 1/4 second before midnight Origin of life (3. 63. 8 billion years ago) First fossil record of animals Plants begin invading land Evolution and expansion of life Fig. 4 -3, p. 84

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

EVOLUTION, NATURAL SELECTION, AND ADAPTATION Ø Biological evolution 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.

The Theory Evolution Theory- the idea that all species descended from earlier, ancestral species l l Explains HOW life has changed and why life is so diverse l Gene Pool- a populations’ genetic make-up (all the genes found in the individuals in a population) Microevolution- small genetic changes that occur in a population l Macroevolution- long-term, large scale changes; cause 2 outcomes: l 1) 2) New species are formed from ancestral species Other species are lost through extinction

How Evolution Occurs l Mutation- a random change in the structure (alleles) or number of DNA molecules in a cell; 99% fatal; Mutagens-radiation (gama, x-ray, UV) or natural or manmade chemicals 2. Abnormalities- mistakes made during the copy process when cells divide or during reproduction 1. l Natural Selection- the process through which some individuals exhibit traits that increase their chances of survival and ability to produce offspring; 3 required conditions Variability of trait in species 2. Must be heritable, able to be passed from one generation to another 3. Differential Reproduction- increase the number of offspring or survivability of offspring of an individual 1.

Adaptation l Natural Selections Causes (1) alleles or sets of alleles that are beneficial to become more common in successive generations and (2) other less beneficial alleles to become less common l Adaptation- the improved ability of an organism to survive and reproduce; a specific trait that increases these chances is called and adaptive trait; often caused by the environment and do one of the following: 1. 2. 3. Species adapt through natural selection Migrate to another area Become extinct

Natural Selection and Adaptation: Leaving More Offspring With Beneficial Traits Ø Three conditions are necessary for biological evolution: 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.

Snail coloration best adapted to conditions Average New average Natural selection Previous average Number of individuals Directional Natural Selection Average shifts Coloration of snails Proportion of light-colored snails in population increases Directional Selection

Light snails eliminated Dark snails eliminated Natural selection Number of individuals Stabilizing Natural Selection Snails with extreme coloration are eliminated Coloration of snails Average remains the same, but the number of individuals with intermediate coloration increases Stabilizing Selection

Intermediate-colored snails are selected against Light coloration is favored Dark coloration is favored Natural selection Number of individuals Diversifying Natural Selection Snails with light and dark colors dominate Coloration of snails Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases Disruptive Selection

Natural Selection l Coevolution- the hypothesis that the population of two interacting species (over a long-term) can cause changes in the gene pool that affect changes in the gene pool of the other species Fig. 5 -5 p. 101

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. 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 Evolution through Natural Selection Ø Evolution through natural selection is about the most descendants. l l 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 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 Ø Each species in an ecosystem has a specific role or way of life. 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

Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Ruddy turnstone Herring gull is a searches tireless scavenger under shells and pebbles Dowitcher probes deeply for small into mud in search of invertebrates snails, marine worms, and small crustaceans Brown pelican dives for fish, which it locates from the air Black skimmer seizes small fish at water surface Louisiana heron wades into water to seize small fish Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation (Birds not drawn to scale) 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 Fig. 4 -8, pp. 90 -91

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

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.

Speciation, Extinction, and Biodiversity Ø Speciation Ø Geographic isolation Ø Reproductive isolation

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

Extinction Ø Background extinction- due to environmental changes; occurs slowly Ø Mass extinction- catastrophic and or widespread; Ø Adaptive radiation- occurs just after a mass extinction when many niches are available in the changed environment

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 1 Make Modified Gene E. coli Cell Extract DNA Gene of interest DNA Identify and remove portion extract gene with of DNA with desired trait Extract Plasmid Genetically modified plasmid Insert modified plasmid into E. coli Plasmid Remove Insert extracted plasmid (step 2) into plasmid from DNA of (step 3) E. coli Grow in tissue culture to make copies Fig. 4 -14, p. 95

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

How Would You Vote? Ø Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available? l l a. No. Human cloning will lead to widespread human rights abuses and further overpopulation. b. Yes. People would benefit with longer and healthier lives.

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.

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).