Biodiversity • Biological Diversity or Biodiversity, is the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystems processes such as energy flow and nutrient cycling.
Biodiversity • Biodiversity • increases with speciation • decreases with extinction • Give-and-take between speciation and extinction changes in biodiversity
Why Biodiversity is important? • It supplies us with food, wood, energy, medicines,… • It preserves the air and water quality and maintains the fertility of soils. • It helps us to dispose of wastes and to control populations of pests
In carrying out these free ecological services, which are also part of the earth’s natural capital, biodiversity helps to sustain life on the Earth.
Idea • Early Greek philosophers • Wallace and Darwin (1858) independently proposed the concept of natural selection as a mechanism for biological evolution’ • But Darwin gathered evidence and publish it in 1859 in his book, On the Origin of Species by Means of Natural Selection
Charles Darwin • 1809-1882 • British naturalist • Proposed the idea of evolution by natural selection • Collected clear evidence to support his ideas
Darwin’s Observations • Most species produce more offspring than can be supported by the environment • Environmental resources are limited • Most populations are stable in size • Individuals vary greatly in their characteristics (phenotypes) • Variation is heritable (genotypes)
Darwin’s finches • 13 species of finches in the Galápagos Islands • Was puzzling since only 1 species of this bird on the mainland of South America, 600 miles to the east, where they had all presumably originated
Darwin’s finches • Differences in beaks • associated with eating different foods • adaptations to the foods available on their home islands • Darwin concluded that when the original South American finches reached the islands, they adapted to available food in different environments
What did Darwin say? • Organisms reproduce more than the environment can support • some offspring survive • some offspring don’t survive • competition • for food • for mates • for nesting spots • to get away from predators
Survival of the fittest • Who is the fittest? • traits fit the environment • the environment can change, so who is fit can change Peppered moth
According to this theory, life has evolved into six major groups of species, called Kingdoms. • Tree of life (development of life)
At any given moment (e.g. the ‘present’), all we see is current diversity…all extinct forms are gone (99.9%) Time
Lamarck • Lamarck’s theory stated that organisms evolve over time due to the environmental factors that act upon that organism • If they began to use an organ more than they had in the past, it would increase in its lifetime. • Meanwhile organs that organisms stopped using would shrink.
Fossil Record: • The world’s cumulative body of fossils found. • Fossils: Mineralized or petrified replicas of skeletons, bones,… or impressions found in rocks • Strongest evidence for evolution
Main cause of evolutionary change: • Mutation: random changes in the structure or number DNA molecules in a cell that can be inherited by offspring. • Mutations can occur in any cell, but only those taking place in reproductive cells are passed on to offspring. • New genetic traits that give better chances for survival (now or in the future)
Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with theses traits (natural selection)
Adaptation • An adaptation or adaptive trait, is any heritable trait that enables and individual organism to survive through natural selection and to reproduce more than other individuals under prevailing environmental conditions
For natural selection to occur,… • The trait must be heritable. • The trait must lead to differential reproduction, which enables individuals with the trait to leave more offspring than other members of the population.
Genetic Resistance • Genetic resistance is the ability of one or more organisms in a population to tolerate a chemical design to kill it. (Ex. Bacteria)
Natural Selection acts in individuals, but evolution occurs in populations
When environmental conditions change: • A population of a species faces 3 possible futures: • Adapt • Migrate • Become extinct
Humans • Page 83
How long does it takes? • Populations of genetically diverse species that reproduce quickly often adapt to a change in short time. • Species that cannot reproduce large numbers of offspring rapidly, take long time to adapt.
3 Common myths • Survival of the fittest means survival of the strongest. • Organisms develop certain traits because they need or want them. • Evolution by natural selection involves some grand plan of nature in which species become more perfectly adapted.
Speciation • Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large number of species, and created opportunities for the evolution of new species.
Speciation When a group becomes geographically isolated over time it will become reproductively isolated = new species formed. • One species can evolve into two or more species • 2 step process • Geographical isolation • Reproductive isolation
Ammospermophilus spp Geographic isolation • When a population becomes divided by a natural barrier. • Mountains, river, body of water, landslides • Groups can’t interbreed or intermix • Become adapted to a different environment Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel
Reproductive Isolation • Differences in isolated groups become so great, they can no longer interbreed • Physical changes • Behavioral changes • Biochemical changes
Howlongdoesittakesthespeciation? • For some rapidly reproducing organisms, this may occur within hundreds of years. • For most species, it takes from tens of thousands to millions of years.
Extinction • Extinction of a species occurs when it ceases to exist; may follow environmental change - if the species does not evolve • Evolution and extinction are affected by: • large scale movements of continents • gradual climate changes due to continental drift or orbit changes • rapid climate changes due to catastrophic events
Extinction: Lights Out • Extinction occurs when the population cannot adapt to changing environmental conditions. • The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4-11
Extinction • Background extinction - species disappear at a low rate as local conditions change • Mass extinction - catastrophic, wide-spread events --> abrupt increase in extinction rate • Five mass extinctions in past 500 million years
Howmanymassextintions? • Some biologists argue that a mass extintions should be distinguished by a low speciation rate as well as by a high rate of extintion. • Under this: only 3 mass extintions.
A mass extintion provides an opportunity for the evolution of new species that can fill unoccupied ecological roles or newly created ones.
Species Diversity: Richness vs. Evenness Species Richness: measurement of the number of species in a given area Species Evenness: measurement of how evenly distributed organisms are among species Community A Community B species 1 25 1 species 2 0 1 species 3 25 1 species 4 25 1 species 5 25 96
Species richness appears to increase the productivity and stability or sustainability of an ecosystem. • While there may be some exceptions to this, most ecologists now accept this as a useful hypothesis
Niche is the species’ occupation and its Habitat location of species (its address)
Niche A species’ functional role in its ecosystem; includes anything affecting species survival and reproduction • Range of tolerance for various physical and chemical conditions • Types of resources used • Interactions with living and nonliving components of ecosystems • Role played in flow of energy and matter cycling
Scientists use theniches of speciestoclassifythembroadly as:GeneralistspeciesSpecialistsspecies
Types of Species • Generalist • large niches • Live in many places • Eat a variety of food • tolerate wide range of environmental variations • do better during changing environmental conditions • Such as flies, cockroaches, mice, rats, humans,…
Types of Species • Specialist • narrow niches • May be able to live in only one type of habitat • Use one or a few types of food • Tolerate a narrow range of climatic and other environmental conditions • more likely to become endangered • do better under consistent environmental conditions • Such as tiger salamanders, China´s giant panda
Fig. 4-7, p. 91 Specialist species with a narrow niche Generalist species with a broad niche Niche separation Number of individuals Niche breadth Region of niche overlap Resource use Fig. 4-7, p. 91
Generalist Species • Page 92
Any given species may play one or more of five important roles- native, nonnative, indicator, keystone, or fundation roles – in a particular ecosystem.