Evolution and BiodiversityEvolution and Biodiversity

Chapter 3Pages 46-62

Evolution: All speciesdescended from earlierancestral species.

Changing genetic make-up in a population over time.

Accepted scientificexplanation of howanimals adapt and survive

Evolution and AdaptationEvolution and Adaptation

• Macroevolution – long term, large scale changes

• Microevolution – small genetic changes • Gene pool – all genes in a population• Mutation – random change in structure

of DNA. Every so often, a mutation is beneficial for survival.

• Natural selection – individuals that have traits that benefit survival.

Natural SelectionNatural Selection

• Microevolution is changes in the gene pool of a population over time that result in changes to the varieties of individuals in a population such as a change in a species' coloring or size.

• Macroevolution If the changes are over a very long time and are large enough that the population is no longer able to breed with other populations of the original species, it is considered a different species.

Evolution and AdaptationEvolution and Adaptation

Microevolution Macroevolution

Natural SelectionNatural Selection

Three things must happen:

• 1. Genetic variability in a trait within population

• 2. Trait is heritable

• 3. Differential reproduction – must enable individuals with the trait to leave more offspring than others without the trait.

• Adaptive (heritable) trait helps survival and reproduction under current conditions

Ecological Niches and AdaptationEcological Niches and Adaptation

• Ecological niche – role in ecosystem. Includes interaction with biotic and abiotic factors.

• Habitat – physical location

• In other words:– Niche – species occupation– Habitat - address

Ecological NichesEcological Niches

Stratification of niches, habitats allows many different species to coexist. This is biodiversity.

Broad and Narrow NichesBroad and Narrow Niches

• Generalist species• Specialist species

– What is better? Depends…• Environmental conditions consistent – favors

specialists. Fewer competitors, food plentiful

• Rapidly changing environmental conditions – favors generalists… More adaptable.

Ecological Niches and AdaptationEcological Niches and Adaptation

Speciation, Extinction, and BiodiversityHow Species Evolve

Speciation, Extinction, and BiodiversityHow Species Evolve

• Speciation• Geographic

isolation

• Reproductive isolation

Fig. 5-7 p. 94

ExtinctionExtinction

• When Environmental changes occur, species must evolve to adapt. If not…

• Background extinction – slow rate• Mass extinction – quickly, large groups• Mass depletion – higher than mass (Ice Age)

– 99% of species that have existed on earth are now extinct.

Changes in Earth’s biodiversity – has leveled off during the last 1.8 millionYears. Is this due to human influence?

ExtinctionExtinction

• Adaptive radiation – after mass extinctions, numerous new species evolve to fill vacated niches. Takes 1-10 million years for adaptive radiation to rebuild biodiversity.

• Human impacts – accelerated extinction

Human Impacts on EvolutionHuman Impacts on Evolution• Artificial Selection – artificially selecting

superior genetic traits• Agriculture• Hatcheries• pets

Genetic Engineering• Gene splicing• Species creation in laboratories• Takes less time than artificial selection

• Concerns about Genetic Engineering• Many failures (1% success rate)• Lead to more abortions? Only for the wealthy?

Biomes: Life on LandBiomes: Life on Land

• major vegetation types on land – based on different climates and atmospheric conditions

• forests, grasslands, deserts• tropical, temperate, polar• temperature and precipitation

determine overall patterns

– What biome do we live in?

Biomes across 39th parallel

Altitude and latitude Altitude and latitude

The two most important factors influencing vegetation in the formation of biomes are precipitation and temperature.

Aquatic Life ZonesAquatic Life Zones

Aquatic Life Zones: Saltwater71% of the Earth

Aquatic Life Zones: Saltwater71% of the Earth

• Coastal zone– majority of marine species (90%)

• most commercial fisheries and interaction with land and humans

• Open ocean– 90% of ocean area

• Estuary– where rivers meet ocean

• Coral reefs and mangrove forests

Ocean ZonesOcean Zones

Freshwater Life ZonesFreshwater Life Zones

• Standing water • Flowing water

Types of Lakes: OligotrophicTypes of Lakes: Oligotrophic

Types of Lakes: EutrophicTypes of Lakes: Eutrophic

Stream SystemsStream Systems

• Runoff• Watershed

• Drainage basin• Floodplain Estuary