Evolution and Biodiversity Chapter 4 Evolution and Biodiversity

Earth: The Just-Right, Adaptable Planet, temp. w/in a narrow range (10-20 C) Distance to sun-perfecto O2 just right Ozone! Diversity and sustainability! 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

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 DNA analysis Figure 4-4

Fossils

Why is the fossil record incomplete? 1. Not all fossils have been found 2. Some fossils have decomposed 3.Some forms of life left no fossils

Chemical analysis

Ice core samples

DNA Analysis

EVOLUTION Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations. It takes time!

Natural Selection and Adaptation: Leaving More Offspring With Beneficial Traits Three conditions are necessary for biological evolution: 1.Genetic variability 2. traits must be heritable 3. 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. http://www.youtube.com/watch?v=elBEeqJQEW0

Adaptation

MUTATION!!!! -can happen from: 1. Genetic variability? MUTATION!!!! -can happen from: X-ray, radioactivity, UV light, chemicals, or it can be a random natural event  Can be harmless, harmful or beneficial. (What happens when a mutation is beneficial?)

2. Traits must be heritable??? BIG BICEPS-NOT REALLY HERITABLE HERITABLE !!!!

3. Differential reproduction. Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do.

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. Evolution: Library: Ancient Farmers of the Amazon This often happens between predators and prey species. Evolution: Library: Toxic Newts

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

HYBRID

Common Myths about Evolution through Natural Selection Survival of the fittest does not mean survival of the strongest! It’s all about who has the most reproductive success Organisms do not develop certain traits because they need them. (ex giraffe) 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

Northern Hemisphere Ice coverage 18,000 years before present Northern Hemisphere Ice coverage Modern day (August) Note: Modern sea ice coverage represents summer months Legend Continental ice Figure 4.6 Changes in ice coverage in the northern hemisphere during the past 18,000 years. (Data from the National Oceanic and Atmospheric Administration) Sea ice Land above sea level Fig. 4-6, p. 89

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

Specialist species Generalist species with a narrow niche with a broad niche Niche separation Number of individuals Figure 4.7 Overlap of the niches of two different species: a specialist and a generalist. In the overlap area, the two species compete for one or more of the same resources. As a result, each species can occupy only a part of its fundamental niche; the part it occupies is its realized niche. Generalist species such as a raccoon have a broad niche (right), and specialist species such as the giant panda have a narrow niche (left). Niche breadth Region of niche overlap Resource use Fig. 4-7, p. 91

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 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

SPECIATION, EXTINCTION, AND BIODIVERSITY Speciation: A new species can arise when members 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

matches snow for camouflage. Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage. Arctic Fox Northern population Early fox Population Spreads northward and southward and separates Different environmental conditions lead to different selective pressures and evolution into two different species. Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern Population Figure 4.10 Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation. Gray Fox Fig. 4-10, p. 92

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

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

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).