<p>* Evolution, Biodiversity and Population Ecology * Chapter 3 * After this lecture, you will be able to: * Explain the process of natural selection and cite evidence for this process * Describe the ways in which evolution influences biodiversity * Discuss reasons for species extinction and mass extinction events * List the levels of ecological organization * Outline the characteristics of populations that help predict population growth * Assess logistic growth, carrying capacity, limiting factors, and other fundamental concepts in population ecology * Evolution is the wellspring of biodiversity * Evolution simply means change over time * Biological evolution is genetic change in populations over time * These genetic changes lead to changes in appearance, functioning, or behavior over generations * Natural selection * Evolution may be random or can be driven by natural selection * Natural selection is the process whereby inherited characteristics that enhance survival and reproduction are passed on more frequently to future generations than those that do not * Evolution by natural selection</p><p>* Evidence of natural selection is everywhere * Artificial selection is the process of selection conducted under human direction * Artificial selection * Natural selection shapes organisms * Premises of natural selection: * Organisms struggle to survive and reproduce * They produce more offspring than can survive * Individuals of a species vary in their characteristics because of genes and the environment * Some individuals are better suited to their environment and reproduce more effectively * Natural selection acts on genetic variation * Populations (NOT individuals) adapt to the environment * A parent that produces more offspring passes on more genes to future generations * Over time, characteristics (traits) that lead to better reproductive success become more prevalent * Adaptive trait (adaptation): a trait that promotes reproductive success * Sexual reproduction also leads to genetic variation * Producing new combinations of genes * Environmental conditions determine the pressures of natural selection * Organisms need time to adapt to changing conditions * Resolving religion and evolution * Literal biblical account is not compatible with evolution * What we know is not compatible with biblical account * E.g., species are unchanging * Many religions accept evolution</p><p>* Speciation * Given enough geographical isolation or selective pressure (from natural selection), members of a population become so different from their ancestors that they may be considered an entirely new species * Speciation produces new types of organisms * The process of generating new species from a single species * Allopatric speciation occurs when species form as a result of physical separation of populations * Main mode of speciation * Populations can be separated by glaciers, rivers, mountains * Each population, with its own set of mutations, diverges</p><p>* Speciation results in diverse life forms * Phylogenetic trees are branching diagrams show relationships among species, groups, genes, etc. * Represent life’s history * Convergent evolution * Similar conditions lead to similar adaptations * Species look alike even if they are not related * Divergent evolution * Species evolve into different types to take advantage of opportunities in environment and reduce competition * Respiration produces energy from</p><p>* water, carbon dioxide, and sugar. * Sugar and oxygen. * oxygen, carbon dioxide, and sugar. * carbon dioxide, enzymes, and sugar. * oxygen, water, and sugar. * Producers rely on ______to capture chemical energy and consumers rely on ______to release chemical energy.</p><p>* cellular respiration; photosynthesis * cellular respiration; cellular respiration * photosynthesis; cellular respiration * photosynthesis; photosynthesis * the sun; the sun * ______drives the hydrologic cycle by producing rain and snow from evaporated surface water. </p><p>* Lunar tides * The Coriolis Effect * Hurricanes * Solar energy * none of the above * Fossil fuels and living trees are known as “carbon sinks” because * they have no carbon. * they create carbon. * they destroy carbon. * they store carbon. * due to gravity, carbon is found closer to the ground. * Evolution occurs as a result of * the discovery of a desirable characteristic in a population. * better survival or reproduction rates by individuals with a particular genetic characteristic. * an individual’s physiological modification. * environmental change that forces modification in a resident species. * a population’s physiological modification * Fossils show life’s history * A fossil is an imprint in stone of a dead organism * Phylogenetic trees and the fossil record show: * Life has existed on Earth for 3.5 billion years * Life evolved complex structures from simple ones * Life evolved large sizes from small ones * But natural selection can also favor simplicity and small size * Extinction * Most species that once lived are now gone * Extinction is the disappearance of a species from Earth * Species last 1–10 million years * Biological diversity is now being lost at an astounding rate * This loss of species is irreversible * Some species are vulnerable to extinction * Extinction occurs when the environment changes rapidly * Many factors cause extinction: * Climate change, changing sea levels, severe weather * Arrival of new species, small populations * Specialized species * Endemic species exist only in a certain, specialized area * Very susceptible to extinction * These species usually have small populations * Island species * Earth has had several mass extinctions * Background extinction rate: extinction usually occurs slowly, one species at a time * Mass extinction events killed off massive numbers of species at once * Occurred five times in Earth’s history * 50–95% of all species went extinct at one time * Cretaceous-Tertiary (K-T) event: 65 million years ago * A gigantic asteroid caused dinosaur extinction * End-Permian event: 250 million years ago * 75–95% of species went extinct * The sixth mass extinction is upon us * Humans are causing the sixth mass extinction event * Population growth, development, resource depletion * Destruction of natural habitats * Hunting and harvesting of species * Introduction of non-native species * This loss affects humans * We need organisms for food, fiber, medicine, services * Amphibians are disappearing faster than any other group * 170 species have already vanished * We study ecology at several levels * Ecology studies interactions among organisms and their environment * Ecology and evolution are tightly intertwined * Species to ecosystems * A species is a “type” of organism * A population is all members of a species living in a given area at the same time * A community consists of all of the populations of organisms living and interacting in a particular area * An ecosystem is the biological community and its physical environment * Species * Populations * Community * Ecosystem * Levels of ecological studies * Organismal ecology examines relationships between individuals and their environment * Population ecology investigates population changes * The distribution and abundance of individuals * Why some populations increase and others decrease * Community ecology focuses on patterns of species diversity and interactions * Ecosystem ecology studies living and nonliving components of systems to reveal patterns * Nutrient and energy flows * Each organism has habitat needs * A habitat is the environment where an organism lives * It includes living and nonliving elements * Species use different criteria to select habitat * Soil, topography, vegetation, other species * Species have different habitat needs * Depending on body size, season, etc. * Species survival depends on having suitable habitats * The niche * A niche is an organism’s use of resources * Along with its functional role in a community * Habitat use, food selection, role in energy and matter flow, interactions with other individuals * Specialists have narrow niches and specific needs * Extremely good at what they do * But vulnerable when conditions change * Generalists are species with broad niches * They use a wide array of habitats and resources * Survive in many different places * Population * Populations can be described by vital statistics or demographics * Size * Age structure * Sex ratio * Density * Distribution * Population size * Number of individuals that contribute to a population’s gene pool * Immigration & Births add individuals * Emigration & Deaths subtract individuals * Population density * Population density is the number of individuals in a population per unit area * Large organisms usually have low densities * They need many resources and a large area to survive * High densities make it easier to find mates * But increase competition and vulnerability to predation * Also increase transmission of diseases * Low densities make it harder to find mates * But individuals enjoy more space and resources</p><p>* Population distribution * Population distribution (dispersion) is the spatial arrangement of organisms * Random - haphazardly located individuals, with no pattern * Resources are widespread * Uniformn - evenly spaced individuals * Territoriality, competition * Clumped - most common in nature * Arranged according to resources * Sex ratios and age structure * Sex ratio is the proportion of males to females * In monogamous species, a 1:1 sex ratio maximizes population growth * Age structure (distribution) is the relative numbers of organisms of each age in a population * Helps predict population growth or decline * In species that continue growing as they age * Older individuals reproduce more (e.g., a tree) * Experience makes older individuals better breeders * Population age structure * Divide population into age categories * Four factors of population growth or decline * Natality - the births within the population * Mortality - deaths within the population * Immigration - arrival of individuals from outside the population * Births and immigration add individuals to a population</p><p>* Emigration - departure of individuals from the population * Deaths and emigration remove individuals * Population growth rate * Growth rate is the rate of change in a population’s size per unit time * Equals (birth rate + immigration rate) – (death rate + emigration rate) * Tells us the net changes in a population’s size per 1000 individuals per year * Growth rate is expressed as a percent * Exponential population growth * In exponential growth, a population increases by a fixed percent * Graphed as a J-shaped curve * It occurs in nature with: * Small populations * Low competition * Ideal conditions * Limiting factors restrain population growth * Exponential growth rarely lasts * Limiting factors: physical, chemical, and biological attributes of the environment limiting population growth * Environmental resistance is all limiting factors together * Stabilizes the population size at its carrying capacity * Terrestrial animals -space, food, water, mates, shelter, breeding sites, temperature, disease, predators * Plants- sunlight, moisture, soil chemistry * Aquatic systems - salinity, sunlight, temperature, etc. * Carrying capacity * Carrying capacity is the maximum population size the environment can sustain * Determined by limiting factors * Limiting factors slow and stop exponential growth * Forms an S-shaped logistic growth curve * Population density affects limiting factors * Density-dependent factors are limiting factors whose influence is affected by population density * Increased density increases the risk of predation, competition for mates, and disease * Results in the logistic growth curve * Environmental resistance has a stronger effect on larger populations * Density-independent factors are limiting factors whose influence is not affected by population density * Temperature extremes, floods, fires, and landslides * Carrying capacities can change * Environments are complex and ever-changing * The carrying capacity can change * Humans lower environmental resistance for ourselves * Increasing our carrying capacity * Technologies have overcome limiting factors * We have appropriated immense amounts of resources * But by increasing the carrying capacity for humans * We have reduced the carrying capacity for countless other organisms * Calling into question our own long-term survival * Conserving biodiversity * Human development, resource use, and population pressure are changing populations and communities * Factors threatening biodiversity have complex social, economic, and political roots * We must understand these factors to solve problems * Millions of people are working to protect biodiversity and to safeguard ecological and evolutionary processes</p><p>* Costa Rica’s protection is paying off * Costa Rica was losing forests at the world’s fastest rate * Now, 25% of its area is under protection * Ecotourism is when tourists visit protected areas * Ecotourism provides thousands of jobs and billions of dollars to Costa Rica’s economy </p>