Evolution and Biodiversity
Chapter 3
Pages 46-62
Evolution: All species
descended from earlier
ancestral species.
Changing genetic makeup in a population over
time.
Accepted scientific
explanation of how
animals adapt and
survive
Evolution 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 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 Adaptation
Microevolution
Macroevolution
Natural 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 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 Niches
Stratification of niches, habitats allows many different
species to coexist. This is biodiversity.
Broad 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 Adaptation
Speciation, Extinction, and Biodiversity
How Species Evolve
• Speciation
• Geographic isolation
• Reproductive isolation
Fig. 5-7 p. 94
Extinction
• 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 million
Years. Is this due to human influence?
Extinction
• 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 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 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
The two most important factors influencing vegetation in the
formation of biomes are precipitation and temperature.
Aquatic Life Zones
Aquatic Life Zones: Saltwater
71% 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 Zones
Freshwater Life Zones
• Standing water
• Flowing water
Types of Lakes: Oligotrophic
Types of Lakes: Eutrophic
Stream Systems
• Runoff
• Watershed
• Drainage basin
Estuary
• Floodplain