Biodiversity and Evolution

Biodiversity and Evolution Chapter 4

4-1 What Is Biodiversity and Why Is It Important? • Concept 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.

Natural Capital: Major Components of the Earth’s Biodiversity Fig 4.2

Why Should We Care About Biodiversity? • Aesthetic pleasure • Ecological: (environmental monitor, ecological balance – keystone species) • Educational • Historical or cultural • Natural Services: (air and water purification, soil fertility, waste disposal,) • Recreational • Medicine • Agriculture: (biological pest control, food source, commercial product – wood) • Moral or ethics

4-2 Where Do Species Come From? • Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations. • Concept 4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

ORIGINS OF LIFE • 1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change.

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

Animation: Evolutionary Tree of Life PLAY ANIMATION

Six Major Kingdoms of Species as a Result of Natural Selection Fig 4.3

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

The Genetic Makeup of a Population Can Change • Populations evolve by becoming genetically different • Genetic variations • First step in biological evolution • Occurs through mutations in reproductive cells • Mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring • Natural selection: acts on individuals • Second step in biological evolution • Adaptation may lead to differential reproduction • Genetic resistance • When environmental conditions change, populations • Adapt • Migrate • 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.

Evolution by Natural Selection Fig 4.5

Three Common Myths about Evolution through Natural Selection • “Survival of the fittest” is not “survival of the strongest” • Organisms do not develop traits out of need or want • No grand plan of nature for perfect adaptation

Animation: Disruptive Selection PLAY ANIMATION

Animation: Stabilizing Selection PLAY ANIMATION

Animation: Evolutionary Tree Diagrams 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.

4-3 How Do Geological Processes and Climate Change Affect Evolution? • Concept 4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.

Movement of the Earth’s Continents over Millions of Years Fig 4.6

Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years Fig 4.7

4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity? • Concept 4-4A As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity. • Concept 4-4B Human activities can decrease biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

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 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

Geographic Isolation Can Lead to Reproductive Isolation Fig 4.8

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-A

Genetic Engineering:Genetically Modified Organisms (GMO) • GMOsuserecombinant DNA • genes or portions of genes from different organisms.

4-5 What Is Species Diversity and Why Is It Important? • Concept 4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of ecosystems.

Variations in Species Richness and Species Evenness

Species-Rich Ecosystems Tend to Be Productive and Sustainable • Species richness seems to increase productivity and stability or sustainability • How much species richness is needed is debatable

Animation: Speciation on an Archipelago PLAY ANIMATION

Evolutionary Divergence • Each species has a beak specialized to take advantage of certain types of food resource.

4-6 What Roles Do Species Play in Ecosystems? • Concept 4-6A Each species plays a specific ecological role called its niche. • Concept 4-6B Any given species may play one or more of five important roles—native, nonnative, indicator, keystone, or foundation roles—in a particular ecosystem.

Each Species Plays a Unique Role in Its Ecosystem • Ecological niche, niche • Pattern of living • Generalist species • Broad niche • Specialist species • Narrow niche

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.

Specialist Species and Generalist Species Niches Fig 4.11

Specialized Feeding Niches • Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-13

Niches Can Be Occupied by Native and Nonnative Species • Native species • Nonnative species; invasive, alien, or exotic species • May spread rapidly • Not all are villains

Indicator Species Serve as Biological Smoke Alarms • Indicator species • Can monitor environmental quality • Trout • Birds • Butterflies • Frogs

Case Study: Why Are Amphibians Vanishing? (1) • Habitat loss and fragmentation • Prolonged drought • Pollution • Increase in UV radiation • Parasites • Viral and fungal diseases • Climate change • Overhunting • Nonnative predators and competitors

Case Study: Why Are Amphibians Vanishing? (2) • Importance of amphibians • Sensitive biological indicators of environmental changes • Adult amphibians • Important ecological roles in biological communities • Genetic storehouse of pharmaceutical products waiting to be discovered

Life Cycle of a Frog Fig 4.14

Keystone, Foundation Species Determine Structure, Function of Their Ecosystems • Keystone species • Pollinators • Top predator • Foundation species • Create or enhance their habitats, which benefit others • Elephants • Beavers

Biodiversity and Evolution