1. Chapter 7
Biological Diversity

2. Biological Diversity Biological Diversity
The variety of life-forms commonly expressed as the number of species in an area (the genes they contain and the ecosystems they live in)

3. Biological Evolution Biological Evolution (Charles Darwin)
The change in inherited characteristics of a population from generation to generation
Can result in new species

4. Four Processes that Lead to Biological Evolution
Mutation
Natural Selection
Migration
Genetic Shift

5. Mutation A chemical change in a DNA molecule
Affects the expressed characteristics (genotype) when cells or individual organisms reproduce

6. Natural Selection Genetic Variability May allow an organism to adapt
Organisms whose biological characteristics make them better able to survive and reproduce (leave more offspring)
4 Characteristics that allow/cause NS to occur:
Genetic Variability May allow an organism to adapt
Environmental Variability changes to the environment (seasons)
Differential Reproduction those organisms best adapted to the environment will have a better chance to reach reproductive age
Environmental Influence changes to environment over time
Species:
a group of individuals that reproduce with each other

7. Migration
Two population of the same species become geographically isolated from each other for a long period of time. New species evolve from an original species due to this isolation
Ex: land bridge b/w Alaska and Siberia, when the bridge was cut off – new species formed

8. Genetic Drift
Changes in the frequency of a gene in a population due to chance Ex: isolation of bighorn sheep in mountains due to human activities. Isolation is in small groups and therefore a small gene pool. Reduces genetic variability and therefore the ability to adapt to future changes. AND less adaptive characteristics may dominate
Can be a problem for rare or endangered species

9. Genetic Drift Example

10. Basic Concepts of Biological Diversity
Genetic Diversity total # of genetic characteristics of a specific species. (Total # of genes)
Habitat Diversity The different kinds of habitats in a given area
Species Diversity – Three Qualities :
Species Richness – total # of species
Species Evenness – relative abundance of a species
Species Dominance- the most abundant species

13. The Number of Species on Earth
No one knows the exact number
About 1.4 million – 1.8 million species have been identified and named
Insects and plants make up most of these species
Number will increase

14. Why are there so many species??
If species compete for resources, wouldn’t the losers die off ??????
The answer lies in the way they interact
Competition, predation, parasitism, mutualism and commensalism

15. Ecological Niche and Habitat
Habitat: where a species lives
Ecological Niche: The sum of all a species tolerance ranges, under which they can survive in an ecosystem.
The reason more species do not die out from competition is that they have developed a niche, and thus avoid competition

17. Species Engage in 3 Basic Interactions
1. Competition
2. Symbiosis – mutualism & commenselism
3. Predation-Parasitism
Each affect evolution, persistence of a species and the overall diversity of life
Organisms have evolved together and therefore adjusted to one another
Human interventions upset these adjustments

18. Competition
Organisms vie for the same limited resources in an environment – food, nutrients, space, sunlight

19. The Competitive Exclusion Principles
2 species that have exactly the same requirements cannot coexist in exactly the same habitat
Ex) introduction of the gray squirrel into Great Britain

21. Symbiosis
The relationship between 2 organisms that is beneficial to both and enhances each organisms chances of persisting
Obligate symbionts:
a symbiotic relationship between two organisms in which neither by themselves can exist without the other
Ex) stomach of a reindeer

22. Types of Symbiosis
Mutualism – Two organisms interact in a manner that is beneficial to both
Birds removing ticks from the back of a Rhino
Bacteria or protozoa living in the gut of an animal
Commenselism – Two organisms interact and it benefits one, but has no impact on the other
Plants that live on the roots of other plants to obtain more water

23. commensalism

25. Parasitism
One organism gains energy by living on or inside a host organism.
Ticks on mammals
Hookworms inside mammals
Parasites are much smaller than their hosts and rarely kill them

26. Predation An organism feeds on part or all of another organism (prey)
Unique strategies for survival
Pursuit and ambush
Mimicry
Camouflage
Chemical Warfare (poisons)

27. Environmental Factors that affect biodiversity
Increase biodiversity:
Physically diverse habitat
Moderate amts. Of disturbance
Sm. Variation in environmental conditions
High diversity in one trophic level (increase diversity in other levels)
Environment highly modified by life
Middle stages of succession
evolution

28. Environmental Factors that affect biodiversity
Decreases biodiversity:
Environmental stress
Extreme environments
Severe limitations in a supply of an essential resource
Extreme amounts of disturbance
Recent introduction of exotic species
Geographic isolation

29. Interrelationships among climate, geology, soil, vegetation and animals

30. Ecological gradient: change in the relative abundance of a species over an area or a distance