Module 2.1: Biodiversity and Evolution

prelim topic

Biodiversity

• It is the variety in species, the genes they contain, ecosystems, ecosystem processes, such as energy flow and nutrient cycling

Species

• Set of individuals that can mate and produce fertile offspring - every organism is a member of a certain species

• May be generalists with broad niches, or specialists with narrow niches

Ecosystem diversity

• Biomes are major habitations/large ecosystems with distinct climates and species

• Deserts, grasslands, forests, mountains, oceans, lakes, rivers, and wetlands

Niche

• The role the species plays in an ecosystem and everything that affects its survival and reproduction

Habitat

• The geographic location of the species

Generalist species (broad niches)

• These species can live in a wide range of environments; less prone to extinction

Specialist species (narrow niches)

• These species live in only a few types of habitats; more prone to extinction because of their inability to tolerate environmental change

Native species

• These species live and thrive in a specific ecosystem

Nonnative species

• These species immigrate into, or are deliberately or accidentally introduced into an ecosystem

• They can threaten native species through competition for resources, reducing the number of native species

• Can spread rapidly if they find a favorable niche

Indicator species

• These species are sensitive to changes in an ecosystem, they 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

Keystone species

• These 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

Natural Selection / Biological Evolution

• The expression of genetic variation over time by succeeding generations

• Through this, 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

Mutagens

• These are random, occur by exposure to radioactivity, ultraviolet radiation, and chemicals

Heritable traits

• These are genetic changes in reproductive cells that are inherited by offspring

Adaptive traits

• These are heritable traits that give individuals advantages that improve their ability to survive and reproduce

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)

Speciation

• This 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

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

Background Extinction

• An slower extinction rate that existed before human population became significant

• the normal, slow rate of species loss driven by natural environmental shifts, competition, and disease