Chapter 5 Evolution of Biodiversity. Earth is home to a tremendous diversity of species Ecosystem...
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Transcript of Chapter 5 Evolution of Biodiversity. Earth is home to a tremendous diversity of species Ecosystem...
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Chapter 5Evolution of Biodiversity
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Earth is home to a tremendous diversity of
species
•Ecosystem diversity- the variety of ecosystems within a given region.
•Species diversity- the variety of species in a given ecosystem.
•Genetic diversity- the variety of genes within a given species.
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Biological Diversity Biological Diversity
Number, variety and variability of Earth’s organisms- 1.9 million identified
Consists of three components:
Genetic diversity (below)
Species
richness
Ecosystem
diversity
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Fig. 4-2, p. 82
Functional Diversity The biological and chemical processes such as energy flow
and matter recycling needed for the survival of species, communities, and ecosystems.
Ecological Diversity The variety of terrestrial and
aquatic ecosystems found
in an area or on the earth.
Solar energyChemical
nutrients (carbon dioxide, oxygen,
nitrogen, minerals)
Heat
Heat Heat
Decomposers (bacteria, fungi)
Producers (plants)
Consumers (plant eaters, meat eaters)Heat Heat
Genetic Diversity The variety
of genetic material within a species or a population.
Species Diversity The number and abundance of species
present in different communities.
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How Do New Species Evolve?
•Speciation: one species splits into two or more species
•Geographic isolation: happens first; physical isolation of populations for a long period
•Reproductive isolation: mutations and natural selection in geographically isolated populations lead to inability to produce viable offspring when members of two different populations mate
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•Species richness- the number of species in a given area.
•Species evenness- the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals.
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Evolution is the mechanism underlying biodiversity
•Evolution- a change in the genetic composition of a population over time.
•Microevolution- evolution below the species level.
•Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla.
• Natural Selection = the process by which traits that enhance survival and reproduction are passed on more frequently to future generations than those that do not
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Creating Genetic Diversity
•Genes- physical locations on chromosomes within each cell of an organism.
•Genotype- the complete set of genes in an individual.
•Mutation- a random change in the genetic code.
•Phenotype- the actual set of traits expressed in an individual.
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Evolution by artificial and natural selection
•Evolution by artificial selection- when humans determine which individuals breed.
•Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce.
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Darwin’s theory of evolution by natural selection
• Individuals produce an excess of offspring.
•Not all offspring can survive.
• Individuals differ in their traits.
•Differences in traits can be passed on from parents to offspring.
•Differences in traits are associated with differences in the ability to survive and reproduce.
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Evolution by Random Processes
•Mutation- occur randomly and can add to the genetic variation of a population.
•Genetic drift- change in the genetic composition of a population over time as a result of random mating.
•Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size.
•Founder effect- a change in a population descended from a small number of colonizing individuals.
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Speciation and extinction determine biodiversity
•Allopatric speciation- when new species are created by geographic or reproductive isolation.
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•Sympatric speciation- the evolution of one species into two species in the absence of geographic isolation, usually through the process of polyploidy, an increase in the number of sets of chromosomes.
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Sympatric speciation
•Sympatric speciation = species form from populations that become reproductively isolated within the same area
•Feed in different areas, mate in different seasons
•Hybridization between two species
•Mutations
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The pace of evolution
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Evolution shapes ecological niches and determines species distributions
•Range of tolerance- all species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance.
•Fundamental niche- the ideal conditions for a species.
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Niches
•Realized niche- the range of abiotic and biotic conditions under which a species lives. This determines the species distribution, or areas of the world where it lives.
•Niche generalist- species that live under a wide range of conditions.
•Niche specialist- species that live only in specific habitats.
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Adaptive RadiationAdaptive RadiationEmergence of Emergence of numerous species numerous species from a common from a common ancestor introduced to ancestor introduced to new and diverse new and diverse environments-happens environments-happens when a niche opens when a niche opens due to changesdue to changes
Example::
Hawaiian Hawaiian Honeycreepers Honeycreepers
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Natural selection acts on genetic variation
• Directional selection = drives a feature in one direction
• Stabilizing selection = produces intermediate traits, preserving the status quo
• Disruptive selection = traits diverge in two or more directions
If the environment changes, a trait may no longer be adaptive
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Coevolution• Evolutionary change
•One species acts as a selective force on a second species
• Inducing adaptations •that act as selective force on the first
species Example:1.Wolf and Moose2.Acacia ants and Acacia trees2.Yucca Plants and Yucca moths3.Lichen
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Convergent Evolution
Species from different evolutionary branches Species from different evolutionary branches may come to resemble one another if they live may come to resemble one another if they live
in very similar environmentsin very similar environments
Example:Example:
1. Ostrich (Africa) and Emu (Australia).1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)
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Scientific Importance of Genetic Diversity
Genetic Engineering
Incorporation of genes from one organism into a different species
Provided:
New vaccines
More productive farm animals
Agricultural plants with desirable characteristics
Depends on genetic diversity (cannot create genes)
Important to protect this diversity
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Why we need diversity
Example contributions to human life:
Food
Clothing
Shelter
Pollination of crops
Antibiotics and medicines
Biological processes (nitrogen fixation)
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Understanding evolution is vital
• It alters the genetic makeup of a population
• It is important for understanding antibiotic and pesticide resistance, agricultural issues, production, medicines, etc.
• Organisms adapt to their environment and change over time
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Evidence of Evolution
•1. Biogeography
•2. Fossil Record
•3. Taxonomy
•4. Homologous Structures
•5. Comparative Embryology
•6. Molecular Biology
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The Fossil Record
•Fossils- remains of organisms that have been preserved in rock. Much of what we know about evolution comes from the fossil record.
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Science Focus: Species Richness on Islands
• Species equilibrium model, theory of island biogeography
• Rate of new species immigrating should balance with the rate of species extinction
• Island size and distance from the mainland need to be considered
• Edward O. Wilson
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The Five Global Mass Extinctions
•Mass extinction- when large numbers of species went extinct over a relatively short period of time.
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Earth has had several mass extinctions
• Background extinction rate = extinction usually occurs one species at a time
• Mass extinction events = five events in Earth’s history that killed off massive numbers of species at once
• 50-95% of all species went extinct at one time
• Humans are causing the sixth mass extinction event
• Resource depletion
• Population growth
• Development
Adaptive Radiation-- new species evolve during recovery period following mass extinction
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Mass ExtinctionsDate of the Extinction
Event
Percent Species Lost
Species Affected
65 mya
(million
years ago)
85 Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes,
and amphibians were unaffected.
213 mya 44 Marine vertebrates and invertebrates
248 mya 75-95 Marine vertebrates and invertebrates
380 mya 70 Marine invertebrates
450 mya 50 Marine invertebrates
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The Sixth Mass Extinction
•Scientists feel that we are in our sixth mass extinction, occurring in the last two decades.
•Estimates of extinction rates vary widely, from 2 % to 25% by 2020.
• In contrast to previous mass extinctions, scientists agree that this one is caused by humans.
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Characteristics of Endangered Species
Extremely small (localized) range
Requiring a large territory
Living on an island
Having a low reproductive success
Small population size
Low reproductive rates
Requiring specialized breeding areas
Having specialized feeding habitats
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Endangered & Extinct Species
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Endangered & Extinct Species
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Earth’s Biodiversity Hotspots
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Causes of Loss of Biodiversity
•Habitat Loss
•Invasive species
•Climate change
•Pollution
•Overharvesting