Envsci101, Lecture 1, Biodiversity

Evolution

Genetic change in organisms across generations. Is the process by which organisms develop and diversify from earlier forms. May be random (drift0 or selective.

What are the main mechanisms by which biodiversity is generated?

- Define biodiversity Main mechnisms include Evolution (biological); Natural Selection and Speciation. Biological evolution refers to the genetic change in organisms across generations. It is the process whereby organisms develop and diversify from earlier forms. It may be random (drift) or selective (Natural selection). Evidence for evolution include transitional fossil forms, and previous extinctions that tell us that species are changing through time in response to the environment. Also, structural homologies; similar morphological traits derived from a shared ancestor. Also, Artificial selection (selective breeding) which has produced numerous new 'types'. Speciation involves the birth of a new species, thus generates greater biodiversity. Speciation is the formation of a new and distinct species, the mechanism being reproductive isolation. Two types; allopatric (prior GI) and sympatric (no prior GI). Natural selection also generates biodiversity by changing the gene pools of populations overtime. It is the process where organisms with traits enhancing survival in that given environment are more likely to survive and pass on these traits to offspring. This is the main process that brings about evolution. According to Botkin & Keller 2011: 2 other mechanisms of evolution also Mutation and Genetic Drift. Mutations are random changes in genes which control characteristics. Mutation may add variability to the species, or prevent individuals from reproducing with normal offspring of their species, thus forming a new species. Genetic drift is the change in the frequency of a gene in a population due to chance (eg. founder effect).

What is biodiversity? How is it measured?

Biodiversity refers to the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems. Biodiversity is not simply a list, it takes into account function and processes - abiotic and biotic components. It occurs at the genetic level and is hierarchial. Biodiversity is organised using the Linnaeus system of taxonomy and systematics. This involves grouping of organisms according to 'type' in increasingly general groups. This taxonomic naming system enabled a fixed meethod for communication between biologists and scientists. This system however did not take into accoutn change or natural selection, as Linnaeus believe in static state. Domain-->Kingdom-->Phylum-->Class-->Order-->Family-->Genus-->Species Biodivesrity is not randomly arranged in space, thus can be measured. Depends on area of place, the energy available, and the latitude. It can be measured through species richness; how many species in an ecological community, landscape or region. Richness is not random, it is influenced by factors such as climate. It can also be measured through species diversity - the number of different species represented in a community; the effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundance - takes into account relative abundances. Withgott & Brennan 2011: Biodiversity generally measured in terms of its most easily measured component; species diversity, and in particular, species richness. Species diversit can be expressed as species richess (total no of species), species eveness (relative abundance of species) and species dominance (the most abundant species). Botkin & Keller 2011: Biodiversity can also be measured in genetic diversity - the differences in DNA composition among individuals which provides the raw material for adaptation to local conditions. Lastly, biodiversity can be measured in Ecosystem diversity; the no. and variety of ecosystems, which may also include the diversity of biotic communities within some specified area.

What is extinction? Difference between background and mass extinction?

Extinction is the ultimate fate of all species - death of a species. Background refers to the natural rates of extinction. Mass is when rates of extinction greatly elevated. Is it selective. Eg. Dinosaur extinction caused by Gulf of Mexico event - selective to very large animals. Withgott & Brennan 2011: Earth has experienced 5 major mass extinction events, each event eliminating at least 1/2 of Earth's species. Essentially, humans are setting the 6th mass extinction in motion. Today, species loss is accelerating as our growing population and resource consumption put increasing strain on habitats and wildlife.

Value of biodiversity

Intrinsic value: Many people value speices and ecosystems intrinsically (eg. for their complexity, diversity, beauty, spiritual significance). - Greater diversity means stability of the ecosystem. - Ecosystems provide goods and services which are unable to be quantified. - Adaptive capacity.

Biodiversity

Is the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part; includes diversity within species, between species, and of ecosystems. It is not just a life - it takes into account functions and processes - abiotic and biotic components. Biodiversity occrs at a genetic level, and is hierarchial.

Mass extinction

Massive elevation of extinction, occurs in a short period of time. Is thus a rapid and widespread decrease in the amount of life on Earth. This can be contrasted with background extinction - natural rates of extinction.

Species richness

Refers to the number of different species represented in an ecological community, landscape or region - how many species are there? It does not take into account the abundances of species or their relative abundance distribution. Equatorial regions tend to have more richness than polar due to warmer, more favourable temps. Richness is thus not random, it is influenced by factors such as climate.

Speciation

The formation of a new and distinct species. The mechanism that enables speciation is the isolation (reproductive) of the groups of individual from each other. 2 types; Allopatric (prior geographical isolation leading to reprod) and sympatric (no prior geographical isolation).

Natural Selection

The process whereby oragnisms better adapted to their enviro (traits enhancing survival) tend to survive and reproduce more often, passing on these traits. Main process that brings about evolution first fully exponded by Charles Darwin. Eg. Drug resistance: Use of antibiotics causes bottlenecks of individuals with low resistance. End population has high resistance.