Transcript Powerpoint
Biodiversity Biodiversity The variety of Earth’s species, the genes they contain, the ecosystems in which they live, & their functions in energy flow & nutrient cycling Destroying the rain forest for economic gain is like burning a Renaissance painting to cook a meal. ~ E. O. Wilson Three Components What affects biodiversity? Natural Selection/Evolution Speciation Extinction Evolution Change in a species’ genetic makeup over time Natural Selection Individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits Begins with mutations Adaptation Video Resistance A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Normal bacterium Resistant bacterium Most of the normal bacteria die The genetically resistant bacteria start multiplying Eventually the resistant strain replaces the strain affected by the antibiotic Limits to Natural Selection When a change in environmental conditions occurs, a gene/mutation must already occur in the population Reproductive capacity – Fast reproduction = quicker adaptation – Slow reproduction = slow adaptation r Selected Unstable environments Small body size High fecundity Early maturity Short generation time Less parental care K selected Stable environments Large body size Long life expectancy Later maturation Few offspring More parental care Reproductive Strategies R- strategists K-strategists Mature rapidly Mature slowly Short lived Long lived Tend to be prey Tend to be both predator and prey Have many offspring and overproduce Have few offspring Low parental care High parental care Generally not endangered Most endangered species are K-strategists Wide fluctuation in population density (booms and busts) Population stabilizes near carrying capacity Population size limited by density-independent factors (climate, weather, natural disasters, requirements for growth) Density-dependent limiting factors to population growth stem from intraspecific competition and include predation, parasitism, and migration Tend to be small Then to be larger Type III survivorship curve Type I or II survivorship curve Examples: most insects, annual plants, bacteria, rodents Examples: humans, elephants, cacti and sharks Survivorship Curves Show age distribution characteristics of species, reproductive strategies and life history. Reproductive success means how many organisms make it to maturity and reproduce Survivorship Curves Type Descriptions I Late Loss Reproduction occurs fairly early in life. Most deaths occur at the limit of biological life span. Low mortality art birth. High probability of surviving to advanced age. Advances in prenatal care, nutrition, disease prevention and cures mean longer life spans for humans. Examples: humans, annual plants, sheep and elephants. II Constant Loss Individuals in all age categories have fairly uniform death rates. Predations affecting all age categories is primary means of death. Typical of organisms that reach adult stages quickly. Examples: rodents, perennial plants and songbirds. III Early Loss Typical of species that have great numbers of offspring and reproduce for most of their lifetime. Death is prevalent for younger members of the species (environmental loss and predation) and declines with age. Examples: sea turtles, trees, internal parasites, fish and oysters. Speciation One species splits into two of more different species Two mechanisms: 1. Geographic Isolation 2. Reproductive Isolation Geographic Isolation Occurs when a population become physically isolated from one another for a long period of time mountains rivers landslides Reproductive Isolation Differences in isolated groups become so great, they can no longer interbreed – Behavioral changes – Physical changes – Genetic changes Speciation in Action California Salamanders Extinction Two Types 1. Biological – The process in which an entire species ceases to exist Local – A population of a species becomes extinct over a large region but not globally Passenger Pigeon 3-5 billion – first European settlers Last died 1914 – Cincinnati zoo - Martha Caused by – Habitat destruction – Over hunting Endemic Species Species only found in one area • Highly vulnerable to extinction Types of Biological Extinction Background extinction – Species disappearing at a slow rate Mass extinction – Significantly high rate of extinction – 25-95% of global species gone • Largest Permian – 96% of species died – Promotes evolution Endangered Species So few individuals that the species could become extinct – Reasons • • • • • • Habitat loss/fragmentation Loss of keystone species Invasive species Climate change Pollution Overcosumption Keystone Species A species that plays a critical role in ecosystem structure & whose impact on the community is greater than expected based on abundance Removal greatly affects the food web Keystone Species Sea Otters Keystone Species Grey Wolves Invasive Species A non native (introduced) species that adversely affects a habitat they invade ecologically and/or economically Invasive Species Where do they come from? • Horticulture • Conservation • Accidental Invasive Species Characteristics Tolerate a variety of habitat conditions Reproduce rapidly – Short generation time Great competitors – generalist Lack of predators Genetic variability Indicator Species Species that provide early warning signs of damage to an ecosystem Examples: Lichens (air quality) Stoneflies (aquatic – DO) Pika – (climate change) Levels of Diversity Ecosystem Diversity – Different habitats, niches, interactions Species Diversity – Different types of organisms Genetic Diversity – Different genes & combinations within a population Measuring Species Diversity Two components: 1. Species richness • Number of unique species 2. Species evenness • Number of individuals of each species in an area Monoculture Opposite of biodiversity Growing only one species of organism Problem? – disease Which do you think is more diverse? A B Which do you think is more diverse? A B Which do you think is more diverse? A B Leaf Litter