1. Evolution of Biodiversity
Chapter 5
Evolution of Biodiversity

2. 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.

4. 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

5. Genetic Diversity The variety of genetic material within a
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 energy
Chemical nutrients (carbon dioxide, oxygen, nitrogen, minerals)
Heat
Heat
Heat
Decomposers (bacteria, fungi)
Producers (plants)
Figure 4.2: Natural capital.
This diagram illustrates the major components of the earth’s biodiversity—one of the earth’s most important renewable resources and a key component of the planet’s natural capital (see Figure 1-4, p. 9). See an animation based on this figure at CengageNOW. Question: What role do you play in such degradation?
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.
Fig. 4-2, p. 82

6. 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

7. 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.

8. 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

9. 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.

10. 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.

12. 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.

14. 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.

16. Speciation and extinction determine biodiversity
Allopatric speciation- when new species are created by geographic or reproductive isolation.

17. 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.

18. 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

19. The pace of evolution

20. 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.

22. 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.

23. Adaptive Radiation
Emergence of numerous species from a common ancestor introduced to new and diverse environments- happens when a niche opens due to changes
Example:
Hawaiian Honeycreepers

25. 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

26. 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:
Wolf and Moose
Acacia ants and Acacia trees
Yucca Plants and Yucca moths
Lichen

27. Convergent Evolution
Species from different evolutionary branches may come to resemble one another if they live in very similar environments Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)

29. 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

30. Why we need diversity Example contributions to human life: Food
Clothing
Shelter
Pollination of crops
Antibiotics and medicines
Biological processes (nitrogen fixation)

31. 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

32. Evidence of Evolution 1. Biogeography 2. Fossil Record 3. Taxonomy
4. Homologous Structures
5. Comparative Embryology
6. Molecular Biology

33. 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.

34. 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

35. The Five Global Mass Extinctions
Mass extinction- when large numbers of species went extinct over a relatively short period of time.

36. 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

37. Date of the Extinction Event Marine vertebrates and invertebrates
Mass Extinctions
Date 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
380 mya 70
Marine invertebrates
450 mya 50

38. 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.

39. 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

40. Endangered & Extinct Species

41. Endangered & Extinct Species

42. Earth’s Biodiversity Hotspots

43. Causes of Loss of Biodiversity
Habitat Loss
Invasive species
Climate change
Pollution
Overharvesting