Chapter 7 Biological Diversity Biological Diversity Biological Diversity

Chapter 7 Biological Diversity

Biological Diversity • Biological Diversity – The variety of lifeforms commonly expressed as the number of species in an area (the genes they contain and the ecosystems they live in)

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

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

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

Natural Selection • 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

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

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

Genetic Drift Example •

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

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

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

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

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

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

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

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

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

commensalism •

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

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