ENVIRONMENTAL SCIENCE CHAPTER 4: Biodiversity and Evolution

Core Case Study: Why Are Amphibians Vanishing? Read page 59 in text Possible reasons for decline in amphibian numbers: 1. Habitat loss and fragmentation 2. Prolonged drought 3. Increased ultraviolet radiation 4. Parasites 5. Viral and fungal diseases

Core Case Study: Why Are Amphibians Vanishing (cont.)? 6. Pollution 7. Climate change 8. Overhunting 9. Nonnative predators and competitors 10. 33% of all amphibian species face extinction

Sect. 4-1: What Is Biodiversity and Why Is It Important? The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth. Biodiversity: Includes the following: 1. The “variety” of all the earths species. 2. The genes contained in all species. 3. The ecosystems that all species live in. 4. The processes of energy flow & nutrient cycling within ecosystems that sustains life.

Biodiversity Species diversity: The “variety” of all the earths species Species: A set of individuals that can mate and produce fertile offspring Possible 8-100 million species total; (most likely 10-14 million exist) 2 million species have been identified ~50% are found in our endangered tropical rainforests

Biodiversity Genetic diversity: The genes contained in all species 1. Enables life to adapt to dramatic environmental changes Ecosystem diversity: The ecosystems that all species live in 1. Biomes: large terrestrial (land) regions (like forests, deserts & grasslands) that have: a. A distinct climate b. Contain certain species, especially vegetation

Biodiversity Functional diversity: The processes of energy flow & nutrient cycling within ecosystems that sustains life Biodiversity plays vital roles in: 1. natural capita & life sustainability 2. preserving air & water quality 3. maintaining fertility of soil 4. organic decomposition & recycling of nutrients 5. controlling populations of pests

Science Focus: Insects Insects have been around for a long time! Bugs have a bad reputation! They are useful to humans and ecosystems Research: 3 insect species that benefit us Insects play vital roles in sustaining life! 1. Pollinators 2. Natural pest control 3. Renewing soils

4-2 How Does the Earth’s Life Change over Time? Concept to learn in sect. 4.2: 1. 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).

Population Changes over Time Populations change by becoming genetically different over time Genetic variability – mutations 1. Random changes in DNA molecules in genes 2. Can occur spontaneously, due to external agents like radiation 3. Can create a heritable trait

Natural Selection Adaptive traits - genetically favorable traits that increase the probability to survive and reproduce 1. Examples? Trait – heritable and lead to differential reproduction What happens to a species when faced with an unexpected environmental change? 1. Adapt through micro-evolution 2. Migrate to a different place 3. Become extinct

Adaptation through Natural Selection Has Limits Example: Humans are unlikely to micro-evolve and have skin that’s not harmed by UV radiation 1. For this to happen, the desired trait must already be in the gene pool. 2. We would need a much higher reproductive capacity so adaptive traits could be spread rapidly 3. Genetically, it would be necessary for proper male/female allele recombination.

4-3 How Do Geological Processes and Climate Changes Affect Evolution? Concept to learn in sect. 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 micro-evolution of new species.

Plate Tectonics Locations of continents and oceans determine earth’s climate Earthquakes and volcanoes can affect biological evolution by separating populations of a species (called Geographic isolation). 1. Can lead to extinction 2. Can lead to the micro-evolution of a species

Earth’s Long-Term Climate Changes Cooling and warming periods (like the Ice-age) – affect the microevolution and extinction of species 1. Can cause a change ocean levels and therefore the area & contours of land 2. Glaciers will expand and contract. a. Leads to further climate changes Causes opportunities for the micro-evolution of new species Many species can/will go extinct

Science Focus: Earth is Just Right for Life to Thrive Life needs a temperature range that results in liquid water Earth’s orbit: exactly the right distance from sun Earth’s optimal gravity: keeps atmosphere in place Favorable temperature range over earth history has promoted micro-evolution and biodiversity Favorable oxygen level in atmosphere for life to exist

4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity? Concept to learn in sect. 4-4: Human activities decrease the earth’s biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

How do new species micro-evolve? Three Ways: 1. Speciation a. One species splits into two or more species that can no longer breed and produce fertile offspring 2. Geographic isolation a. Different groups of the same population of species become physically isolated from one another for a long period of time b. Causes: streams, earthquakes, volcanos

How do new species micro-evolve? 3. Reproductive Isolation a. As a result of geographic isolation, micro-evolution leading to speciation will allow for genetic changes such that if the original species are re-introduced, they will no longer be “species” that can reproduce fertile offspring

Science Focus: Changing Genetic Traits, page 69 Artificial selection 1. Selective breeding: crossbreeding varieties within same species to enhance desired traits 2. Its done with grains, fruits, vegetables, dogs, & other animals Genetic engineering 1. Add, delete, or alter DNA segments to produce a desirable effect 2. Add desirable genes from other species a. Done to develop new drugs & pest-resistant plants 3. Its very controversial. Why? What are your thoughts?

Extinction Biological extinction Local extinction Endemic species 1. Entire species are completely gone Local extinction All members of a species in a specific area are gone. Could survive if: They adapt to the new environment Possibly migrate to new location Endemic species 1. Species found only in one area 2. Are especially vulnerable to extinction

Extinction Background extinction 1. the slow disappearance of a species 2. Speciation is generally more rapid than extinction Mass extinction: a significant rise in rates beyond background extinction 1. Earth took many years to recover from previous mass extinctions 2. Balance between speciation and extinction determines biodiversity of earth. 3. Usually the result of catastrophic/global event

Human Activities and Extinction Humans have caused the premature extinction of species (will discuss in chapter 8)

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

Species Diversity: an important characteristic of a community & ecosystem Includes both the variety and abundance of a species in a particular place Species richness: the number of different species a place contains Species evenness: the relative abundance of individuals within a species Species types vary with geographic location Species richness declines towards poles, and is highest in the tropics

Richness and Sustainability of Ecosystems Hypothesis: Does a community with high species richness have greater sustainability and productivity? Research suggests “yes” 1. in plant productivity 2. greater numbers of species seems to make ecosystems more stable.

Sect. 4.6: What Roles Do Species Play in an Ecosystem? Concept to learn in sect. 4-6: Each species plays a specific ecological role called its niche.

Ecological Niche Species occupy unique niches and play specific roles in an ecosystem 1. It’s the species “pattern” of living, not its habitat. Includes everything required for survival and reproduction 1. How much water the species requires 2. How much sunlight the species needs How much space is needed Temperature range the species can tolerate 5. Food requirements

Ecological Niche: Used for broad classification of species Two “niche” classifications: 1. Generalist species: a. Have broad niches b. Can live in many places c. Can eat many foods d. Can tolerate wide environmental conditions 2. Specialist species: a. Have narrow niches b. One habitat type c. Limited food/narrow temperature tolerance

Science Focus: Cockroaches One of the longest existing organisms– 3,500 known species Highly adapted, rapidly producing generalists 1. Consume almost anything 2. Can endure food & water shortage 3. Survive everywhere except polar regions 4. Can avoid predation, because of their eyesight & ability to sense vibrations. Carry human diseases (thru viruses & bacteria

Indicator Species: Our biological “Smoke Alarms” Those species that provide an early warning system to an ecosystem Fish (example: trout is sensitive to O2) Birds 1. sensitive to changes made to their environment 2. sensitive to pesticides Butterflies 1. indicate lack of plant species Amphibians (primarily frogs)

Keystone Species: importance to ecosystems Those species that play a significant role in their food web. Have a large affect on types and abundances of other species in an ecosystem Elimination of keystone species may alter structure and/or function of ecosystem Some are pollinators Top predators (regulate #s of other species)

Foundation Species: importance to ecosystems Create and enhance their own habitats in a way that benefits other species and ecosystems Examples: 1. Beavers- build dams for themselves & other species 2. Elephants- knock down trees, allowing for smaller plant species to grow (food for smaller species) 3. Seed dispersers- allow for plant growth

Science Focus: American Alligator (read pg 75) Highly adaptable- documented presence since dinosaurs Only natural predator is humans In 1967 – endangered species list, due primarily to poaching They’ve made a successful environmental comeback (a success story) They are a keystone species: provide habitats for other species

Case Study: Why Should We Protect Sharks? They remove injured and sick animals Many are gentle giants Provide potential insight into cures for human diseases such as cancer They are considered to be keystone species Hunted and killed by humans, out of fear, and for their body parts.