Environmental Science, 15e PDF

Environmental Science, 15e MILLER/SPOOLMAN G. TYLER MILLER | SCOTT E. SPOOLMAN 4 Biodiversity and Evolution © 2016 Cengage Learning....

Environmental Science, 15e MILLER/SPOOLMAN G. TYLER MILLER | SCOTT E. SPOOLMAN 4 Biodiversity and Evolution © 2016 Cengage Learning. All Rights Reserved.  Core Case Study: Why Are Amphibians Vanishing? Amphibians (frogs, toads, and salamanders) show great biodiversity (more than 6,700 species) – Many populations have declined or vanished Why is the loss of amphibian populations significant? Why are pharmaceutical companies interested in the preservation of amphibian species? © 2016 Cengage Learning. All Rights Reserved.  4.1 What Is Biodiversity and Why Is It Important? Sustaining life on the earth depends on the biodiversity found in genes, species, ecosystems, and ecosystem processes © 2016 Cengage Learning. All Rights Reserved.  Biodiversity Is a Crucial Part of the Earth’s Natural Capital Biodiversity is the variety in: – Species (species diversity) – The genes they contain (genetic diversity) – Ecosystems (ecological diversity) – Ecosystem processes, such as energy flow and nutrient cycling (functional diversity) © 2016 Cengage Learning. All Rights Reserved.  Natural Capital: Earth’s Biodiversity © 2016 Cengage Learning. All Rights Reserved.  Biodiversity Includes a Number of Components Species diversity is the number and variety of species in a biological community Genetic diversity is the variety of genes in a population or species © 2016 Cengage Learning. All Rights Reserved.  Genetic Diversity © 2016 Cengage Learning. All Rights Reserved.  Species and Biomes Species – Set of individuals that can mate and produce fertile offspring – every organism is a member of a certain species Ecosystem diversity – Deserts, grasslands, forests, mountains, oceans, lakes, rivers, and wetlands – Biomes are major habitations/large ecosystems with distinct climates and species © 2016 Cengage Learning. All Rights Reserved.  A Variety of Biomes © 2016 Cengage Learning. All Rights Reserved.  4.2 What Roles Do Species Play in Ecosystems? Each species has a specific ecological role called its niche (what the species does) There are four important roles that a species can play in a particular ecosystem – Native – Nonnative – Indicator – Keystone © 2016 Cengage Learning. All Rights Reserved.  Each Species Plays a Role in Its Ecosystem Niche – The role the species plays in an ecosystem and everything that affects its survival and reproduction Habitat – The geographic location of the species Species – May be generalists with broad niches, or specialists with narrow niches © 2016 Cengage Learning. All Rights Reserved.  Generalist and Specialist Species Generalist species (broad niches) – Can live in a wide range of environments; less prone to extinction Specialist species (narrow niches) – Live in only a few types of habitats; more prone to extinction because of their inability to tolerate environmental change Is it better to be a generalist or a specialist? © 2016 Cengage Learning. All Rights Reserved.  A Specialist and a Generalist © 2016 Cengage Learning. All Rights Reserved.  Specialization Reduces Competition © 2016 Cengage Learning. All Rights Reserved.  Native and Nonnative Species Native species – Live and thrive in a specific ecosystem Nonnative species – Immigrate into, or are deliberately or accidentally introduced, into an ecosystem – Can threaten native species through competition for resources, reducing the number native species – Can spread rapidly if they find a favorable niche © 2016 Cengage Learning. All Rights Reserved.  Indicator Species Serve as an Biological Smoke Alarm An indicator species is sensitive to changes in an ecosystem – Provide early warnings of community and ecosystem change – Some amphibian species are good indicator species – their extinction in Central and South American tropical forests has been tied to climate change © 2016 Cengage Learning. All Rights Reserved.  Keystone Species Play Critical Roles in Their Ecosystems Keystone species affect the type and abundance of other species in an ecosystem and can be responsible for: – Pollination of flowering species (butterflies, honeybees) – Regulation of populations of other species (wolves, alligators) – May cause population crashes and extinction of dependent species if drawn to extinction itself © 2016 Cengage Learning. All Rights Reserved.  Case Study: The American Alligator – A Keystone Species The American alligator, a keystone species of subtropical wetland ecosystems – Almost hunted to extinction – so much so it was placed on the endangered species list – Today, it has recovered and been removed from this list Why is this an important success story? What nonnative invader species is now threatening American alligators? © 2016 Cengage Learning. All Rights Reserved.  Case Study: Why Should We Protect Sharks? Sharks, a keystone species, are being degraded by human activities: – Over a million are killed annually in response to exaggerated media reports on shark attacks – Harvested for their fins and for Asian pharmaceutical cure-alls Do you think sharks should be a protected species? © 2016 Cengage Learning. All Rights Reserved.  4.3 How Does the Earth’s Life Change Over Time? The theory of evolution as demonstrated in the process of natural selection – Explains how life on the earth changes over time due to changes in the genes of populations Population evolution occurs through gene mutation – Gives individuals genetic traits that enhance their ability to survive and produce offspring © 2016 Cengage Learning. All Rights Reserved.  Biological Evolution by Natural Selection Explains How Life Changes Over Time Fossils reveal the history of life Biological evolution – The expression of genetic variation over time by succeeding generations (natural selection) – Through natural selection, species evolve over time from earlier ancestral ones – Individuals with traits that increase their survivability are more likely to produce offspring and pass on these traits © 2016 Cengage Learning. All Rights Reserved.  Mutations Are Changes in Genetic Composition (DNA) Some are random; others occur by exposure to radioactivity, ultraviolet radiation, and chemicals (mutagens) Genetic changes in reproductive cells are inherited by offspring (heritable traits) Some heritable traits give individuals advantages that improve their ability to survive and reproduce (adaptive traits) © 2016 Cengage Learning. All Rights Reserved.  Biological Evolution By Natural Selection Depends on Genetic Diversity Genetic resistance – The ability of one or more organisms in a population to tolerate chemicals designed to kill the population – Develops in bacteria and insect species because they rapidly produce large numbers of offspring (antibiotic-resistant bacteria) © 2016 Cengage Learning. All Rights Reserved.  Evolution by Natural Selection © 2016 Cengage Learning. All Rights Reserved.  Adaptation Through Natural Selection Has Limits Limiting factors for adaptation: – Organisms can only adapt to a change in environmental conditions if the necessary genetic traits are already present in a population’s gene pool – Even if a beneficial heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity © 2016 Cengage Learning. All Rights Reserved.  Some Common Myths About Evolution Through Natural Selection “Survival of the fittest” means “survival of the strongest” – For biologists, fittest are those that are most reproductively successful and leave the most descendants, not the strongest physically “Evolution explains the origins of life” – Instead, evolution explains how species developed after life began © 2016 Cengage Learning. All Rights Reserved.  More Common Myths “Humans evolved from apes or monkeys” – Humans, apes and monkeys evolved along different paths from a common ancestor “Evolution by natural selection involves a grand plan of nature in which species are to become more perfectly adapted” – There is no clear path – forces of natural selection and random mutation can push evolution along many different paths © 2016 Cengage Learning. All Rights Reserved.  4.4 What Factors Affect Biodiversity? As environmental conditions change, biodiversity is determined by the balance between formation of new species and the extinction of existing species Human activity has caused loss of biodiversity: – By causing extinction of species – Through degradation of habitats needed for development of new species © 2016 Cengage Learning. All Rights Reserved.  How Do New Species Arise? Speciation occurs when one species splits into two or more different species – Species are considered different when individuals can no longer breed and reproduce fertile offspring © 2016 Cengage Learning. All Rights Reserved.  Geographic and Reproductive Isolation Geographic isolation – Occurs when groups of the same population become physically isolated (by mountains, rivers, roads or distance) from one another over time Reproductive isolation – Occurs when mutation and change by natural selection operate independently in the gene pool of geographically isolated populations © 2016 Cengage Learning. All Rights Reserved.  Geographic Isolation Can Lead to Reproductive Isolation © 2016 Cengage Learning. All Rights Reserved.  How Do Humans Affect Biodiversity? By contributing to the rise of new species through artificial selection – Selectively breed or crossbreed between genetic variations of the same species By using genetic engineering to quickly manipulate genes – Alter segments of DNA for desired traits – Transfer genes between different species that would not interbreed in nature © 2016 Cengage Learning. All Rights Reserved.  All Species Eventually Become Extinct Extinction occurs when a species ceases to exist (biological extinction) A species facing a crisis may: – Adapt to the new changes in the environment – Migrate to a new geographic location that is more suitable to their lifestyle – Become extinct © 2016 Cengage Learning. All Rights Reserved.  Endemic Species Are Very Vulnerable to Extinction Found in only unique geographic areas – making it difficult for them to migrate or adapt during rapidly changing environmental conditions Many endangered endemic species are amphibians © 2016 Cengage Learning. All Rights Reserved.  Background Versus Mass Extinction Background extinction – slower rate that existed before human population became significant Mass extinction – significant rise in extinction over background extinction rate – Often global events tied to major widespread environmental change – Have also occurred as a result of human activity © 2016 Cengage Learning. All Rights Reserved.  A Short History of Mass Extinctions Fossil and geological evidence indicate that there have probably been five mass extinctions during the past 500 million years These mass extinctions have been followed by an increase in species diversity – New species arise to fill unoccupied niches or to exploit newly available ones © 2016 Cengage Learning. All Rights Reserved.  When Will the Next Mass Extinction Occur? Evidence suggests that speciation on average through time has kept ahead of extinction However, scientists now think we may be experiencing the beginning of a new mass extinction that is the result of human activity © 2016 Cengage Learning. All Rights Reserved.  Additional Case Study: The Ivory-Billed Woodpecker – Extinct? Native to southeast U.S. wetlands and forests – Last sighted in the 1940s and was deemed extinct in the mid-1990s – due to deforestation/habitat loss and overhunting – In the early 2000s, Cornell Ornithology Lab scientists searched more than half a million acres over eight states looking for the ivory-billed woodpecker © 2016 Cengage Learning. All Rights Reserved.  Additional Case Study: Ivory-Billed Woodpecker – Sighted No confirmed sightings until 2005 – A single male was sighted (confirmed by the research team and the director of the Cornell Ornithology Lab) How does this case study pertain to biodiversity and extinction? Why should you be concerned about species going extinct? © 2016 Cengage Learning. All Rights Reserved.  The Ivory-Billed Woodpecker and the Three Big Ideas These woodpeckers’ niche involves stripping bark from dead trees to feed on beetle larvae inside the trees – As environmental conditions changed, their habitat was destroyed so thoroughly that they may not have had a chance to genetically adapt to these changes Sometimes organisms deemed extinct are actually rediscovered as still living © 2016 Cengage Learning. All Rights Reserved.