Chapter 8 Biological Diversity and Biological Invasions Overview

Chapter 8: Biological Diversity and Biological Invasions

Overview n n n n What is Biological Diversity? Biological Diversity Basics Biological Evolution Competitive and Ecological Niches Symbiosis Predation and Parasitism How Geography and Geology Affect Biodiversity Invasions, Invasive Species and Island Biogeography

What is Biological Diversity n n Bio diversity refers to the variety of life forms in an area. Expressed 2 ways Number of species in an area n Number of genetic types in an area n

Why Do People Value Nature? n Eight Reasons Utilitarian n Public service n Moral n Theological n Aesthetics n Recreational n Spiritual n Creative n

Biological Diversity Basics n Genetic Diversity n n Habitat Diversity n n Total number of genetic characteristics of a specific species, subspecies, or group of species The different kinds of habitats in a given unit area Species Diversity n n n Species richness - total number of species Species evenness - relative abundance of species Species dominance - the most abundant species

Species Diversity n Counting the number of species is not enough to describe biological diversity n n n Left = 10 species; 100 individuals, 87 elephants, 9 species with 2 individuals each Right = 10 species; 100 individuals, 10 individuals each species Which has greater species richness? Species evenness?

Number of Species on Earth n n n 1. 5 million species have been identified Estimated that almost 3 million different species currently exist All living things categorized into taxa n n n n Kingdom Phylum Class Order Family Genus Species

Biological Evolution n n How did biological diversity come about? Too amazing to have come about by chance Many believed that it must have been created by God n “everything in the world is marvelously ordered by divine providence and wisdom for the safety and protection of us all” -Cicero n

Biological Evolution n Charles Darwin Ninth century n Explanation of diversity known as biological evolution n n Biological Evolution n Change in inherited characteristics of a population from generation to generation

Biological Evolution n New species arise as a result of: Competition for resources n Difference among individuals in their adaptations to environmental conditions n n Four processes lead to evolution Mutation n Natural selection n Migration n Genetic drift n

Mutation n Genes are inherited from one generation to the next Contained in the chromosomes of each cell n Genes made up of DNA n DNA made up bases A, C, G, T n n How these letters are combined determines the “message” interpreted by a cell

Mutation n When cells divide DNA is reproduced n Each new cell gets a copy n n n Mutation - when an error occurs in the reproduction of DNA as it gets passed to new cells Possible causes: radiation or a viruses

Mutation n In some cases offspring with a mutation cannot survive In some cases a mutation simply adds to genetic variability in the species In some cases mutation changes the offspring drastically and a new species is created

5 big factors that decrease biodiversity - HIPPO n n n H= I= P= P= O= Habitat Destruction Introduced Species Pollution Population Growth Over-consumption

Natural Selection n Some individuals may be better suited to the environment than others Those better able to survive and reproduce leave more offspring n Their descendants form a larger proportion of the next generation n n The accumulation of changes may lead to reproductive isolation n Resulting in a new species

Natural Selection n Four primary characteristics Genetic variability n Environmental variability n Differential reproduction that varied with the environment n Influence of the environment on survival and reproduction n

Migration and Geographic Isolation n Two populations become geographically isolated for a long time n n n Differences accumulates so that they no longer reproduce Two new species have formed Migration important evolutionary process (Adaptive Radiation) n Ex: Hawaii honey creeper and Darwin’s finches

Genetic Drift n Genetic drift n n Changes in frequency of a gene in a population simply by chance Founder effect n Small number of individuals are isolated from larger population Less genetic variation than original population n Characteristics present are affected by chance n n Individuals may NOT be better adapted

Interaction between Species n Competition n n Symbiosis n n The outcome is negative for both groups Benefits both participants Predation and parasitism n The outcome benefits one and is detrimental to the other.

Competitive Exclusion Principle n Two species that have exactly the same requirements cannot coexist in exactly the same habitat. n Ex- British Red Squirrel and American Grey Squirrel

Niches: How Species Coexist n Ecological Niche Concept n n Explains how so many species can coexists Example: Flour beetles (Tribolium) n n Specific # of beetles of two species placed in flour Containers maintained at various temp and moisture levels Periodically beetles counted One species always wins but which one depends on conditions

Niches: How Species Coexist n All flour beetles have the same ecological functional niche n n Same “profession” – eating flour Different Flour beetles can live in different habitats

Measuring Niches n Describe the niche n n the set of all environmental conditions under which a species can persist and carry out its life functions Measured Niche Fundamental niche n Realized niche n Ex- flatworms in streams n

Fundamental temperature niche Realized temperature niche

Symbiosis n Describes a relationship between two organisms n n beneficial to both enhances each organism’s chance of persisting Each partner called a symbiont Ex- reindeer and gut bacteria n n Food for reindeer Home for bacteria

Predation and Parasitism n n Relationship is beneficial for predator or parasite and negative for prey or host Predation n n One organism (predator) feeds on other live organisms (prey) Parasitism n One organism (the parasite) lives on, in, or within another (the host)

How Geology and Geography Affect Biologic Diversity n Species are not uniformly distributed over the earth’s surface n n They are not uniformly distributed locally, either Species change with soil type and topography: n slope, aspect (the direction the slope faces), elevation, and nearness to a drainage basin

Biotic Provinces n n In 1876 Wallace suggested that the world could be divided into six biogeographic regions Referred to as realms n Neartic, Neotropical, Palaeartic, Ethiopian, Oriental, and Australian

Biotic Provinces n In each major biogeographic area certain families of animals are dominant and fill ecological niches n For example large herbivores North America - bison and pronghorn n South America - capybara n Australia - kangaroo n Africa - giraffes and antelope n

Biotic Provinces n n Wallace’s realms still valid and extend to all life forms A biotic province is a region inhabited by a characteristic set of taxa, bounded by barriers that prevent emigration and immigration.

Biotic Provinces n W/in a realm n n n Species more likely to be related Evolved and adapted in the same place for a long time When a species introduced may be unrelated or distantly related to native species. n n Ecological and evolutionary adjustments are yet to take place. Introduced species may be superior competitor

Biomes n Similar environments provide similar opportunities and similar constraints Leads to evolution of organisms similar in form and function n Rule of climatic similarity n

Biotic Province vs. Biome n A biotic province is based on who is related to whom n n An evolutionary unit A biome is based on niches and habitat n If we know the climate we can make predictions about the biome

Example of Convergent Evolution- given sufficient time and similar climates species similar in shape and form will tend to occur Joshua Tree Saguaro from North America Euphorbia of East Africa

Ostrich from Africa Rhea from South America Emu from Australia Divergent evolution - population is divided and each evolves separately

Invasions, Invasive Species and Island Biogeography n Island Biogeography Fewer species than continents n Two new sources of species is migration and evolution n Smaller the island the fewer the species n The farther away from a continent the fewer the species n

Island Biogeography n n Small islands tend to have fewer habitat types A small population easily wiped out by a storm, flood, catastrophe or disturbance n n The smaller the population the greater the risk of extinction The farther an island is from the mainland the harder it is to reach

Island Biogeography n Islands tend to maintain consistent number of species over time. n n n Result of the rate at which species added Minus rate at which they become extinct Concept applies to ecological islands n A comparatively small habitat separated from a major habitat of some kind.

Biogeography and People n Biogeography affects biological diversity Changes in biodiversity affect people and resources n Effects extend from individuals to civilizations n

Biogeography and People n People alter biodiversity by Direct hunting n Directly disturbing habitats n Introducing exotic species into new habitats n n Introductions of exotics have mixed results Food sources, landscaping, pets n Disastrous ecological consequences n