Chapter 5 Evolution and Biodiversity

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

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

Core Case Study Earth: The Just-Right, Adaptable Planet  During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of o C. Figure 4-1

ORIGINS OF LIFE  1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change. Figure 4-2

Fig. 4-2, p. 84 Variety of multicellular organisms form, first in the seas and later on land Biological Evolution (3.7 billion years) Chemical Evolution (1 billion years) Formation of the earth’s early crust and atmosphere Small organic molecules form in the seas Large organic molecules (biopolymers) form in the seas First protocells form in the seas Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas

Animation: Stanley Miller’s Experiment PLAY ANIMATION

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

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

Animation: Evolutionary Tree of Life

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. Figure 4-4

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

Animation: Stabilizing Selection PLAY

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

Animation: Disruptive Selection PLAY ANIMATION

Animation: Moth Populations PLAY ANIMATION

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. This often happens between predators and prey species.

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

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. Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

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. Organisms do not develop certain traits because they need them. There is no such thing as genetic perfection. 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 locations of continents and oceanic basins influence climate. The movement of continents have allowed species to move. The movement of continents have allowed species to move.

Fig. 4-5, p million years ago Present 65 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 4-6

Fig. 4-6, p. 89 Land above sea level 18,000 years before present Northern Hemisphere Ice coverage Modern day (August) Note: Modern sea ice coverage represents summer months Legend Continental ice Sea ice

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.

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. 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. 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  Generalist species tolerate a wide range of conditions.  Specialist species can only tolerate a narrow range of conditions. Figure 4-7

Fig. 4-7, p. 91 Generalist species with a broad niche Number of individuals Resource use Specialist species with a narrow niche Niche separation Niche breadth Region of niche overlap

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

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

Fig. 4-8, pp Piping plover feeds on insects and tiny crustaceans on sandy beaches (Birds not drawn to scale) Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Knot (a sandpiper) picks up worms and small crustaceans left by receding tide Herring gull is a tireless 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 4-9

Fig. 4-9, p. 91 Maui Parrotbill Fruit and seed eaters Insect and nectar eaters Kuai Akialaoa Amakihi Crested Honeycreeper Apapane Akiapolaau Unknown finch ancestor Greater Koa-finch Kona Grosbeak

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. Genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited.

Animation: Speciation on an Archipelago PLAY ANIMATION

Animation: Evolutionary Tree Diagrams PLAY ANIMATION

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

Fig. 4-10, p. 92 Different environmental conditions lead to different selective pressures and evolution into two different species. Southern Population Northern population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage. Gray Fox Arctic Fox Spreads northward and southward and separates Early fox Population

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

Fig. 4-12, p. 93 Tertiary Bar width represents relative number of living species EraPeriod Species and families experiencing mass extinction Millions of years ago Ordovician: 50% of animal families, including many trilobites. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites Cambrian Ordovician Silurian Devonian Extinction Paleozoic Mesozoic Cenozoic 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 caused by human activities. Many species are expected to become extinct within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic Jurassic Cretaceous Extinction QuaternaryToday

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

Fig. 4-13, p. 94 Marine organisms Terrestrial organisms Number of families Millions of years ago Quaternary Tertiary Pre-cambrian Cambrian Ordovician Silurian Devonian Carboniferous Jurassic Devonian Permian Cretaceous

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

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

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

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

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

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 Transgenic plants with new traits Transfer to soil Stepped Art

THE FUTURE OF EVOLUTION  Biologists are learning to rebuild organisms from their cell components and to clone organisms. Cloning has lead to high miscarriage rates, rapid aging, organ defects. Cloning has lead to high miscarriage rates, rapid aging, organ defects.  Genetic engineering can help improve human condition, but results are not always predictable. Do not know where the new gene will be located in the DNA molecule’s structure and how that will affect the organism. 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  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. strength, speed, agility. weapons (claws, fangs), protection (shell). weapons (claws, fangs), protection (shell). poor hearing and vision. poor hearing and vision.  We have thrived as a species because of our: opposable thumbs, ability to walk upright, complex brains (problem solving). opposable thumbs, ability to walk upright, complex brains (problem solving).