Evolution and Biodiversity

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?

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?

Rest assured, you are not alone!

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 10-20oC. Figure 4-1

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

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

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

Recorded human history begins about 1/4 second before midnight Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight Recorded human history begins about 1/4 second before midnight Age of mammals Age of reptiles Insects and amphibians invade the land Origin of life (3.6-3.8 billion years ago) Figure 4.3 Natural capital: greatly simplified overview of the biological evolution by natural selection of life on the earth, which was preceded by about 1 billion years of chemical evolution. Microorganisms (mostly bacteria) that lived in water dominated the early span of biological evolution on the earth, between about 3.7 billion and 1 billion years ago. Plants and animals evolved first in the seas. Fossil and recent DNA evidence suggests that plants began invading the land some 780 million years ago, and animals began living on land about 370 million years ago. Humans arrived on the scene only a very short time ago—equivalent to less than an eye blink of the earth’s roughly 3.7-billion-year history of biological evolution. 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? 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 Mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.

The Theory Evolution Evolution Theory- the idea that all species descended from earlier, ancestral species Explains HOW life has changed and why life is so diverse 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 Macroevolution- long-term, large scale changes; cause 2 outcomes: New species are formed from ancestral species Other species are lost through extinction

How Evolution Occurs 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 man-made chemicals Abnormalities- mistakes made during the copy process when cells divide or during reproduction 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 Must be heritable, able to be passed from one generation to another Differential Reproduction- increase the number of offspring or survivability of offspring of an individual

Adaptation 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 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: Species adapt through natural selection Migrate to another area Become extinct

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

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

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

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

Natural Selection Fig. 5-5 p. 101 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

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.

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. Some species (mostly microorganisms) can exchange genes without sexual reproduction. 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.

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.

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.

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

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

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 Piping plover feeds on insects and tiny crustaceans on sandy beaches 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. 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

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.

Speciation, Extinction, and Biodiversity Geographic isolation Reproductive isolation

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

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

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

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

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

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. Figure 4-14

Identify and remove portion of DNA with Phase 1 Make Modified Gene E. coli Genetically modified plasmid Insert modified plasmid into E. coli Cell Extract Plasmid Extract DNA Plasmid Gene of interest DNA Identify and remove portion of DNA with desired trait Remove plasmid from DNA of E. coli Insert extracted (step 2) into plasmid (step 3) Identify and extract gene with desired trait Grow in tissue culture to make copies Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Fig. 4-14, p. 95

Transfer plasmid copies to a carrier agrobacterium Phase 2 Make Transgenic Cell A. tumefaciens (agrobacterium) Foreign DNA E. Coli Host DNA Plant cell Nucleus Transfer plasmid copies to a carrier agrobacterium Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Transfer plasmid to surface of microscopic metal particle Use gene gun to inject DNA into plant cell Fig. 4-14, p. 95

Grow Genetically Engineered Plant Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Figure 4.14 Genetic engineering: steps in genetically modifying a plant. Transgenic plants with new traits Fig. 4-14, p. 95

Grow Genetically Engineered Plant Transgenic cell from Phase 2 Phase 3 Grow Genetically Engineered Plant 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? Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available? 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 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. 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.

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).