Biological Diversity and Biological Invasions Chapter 9 Biological Diversity and Biological Invasions

Biological Diversity and Biological Evolution The variety of life-forms commonly expressed as the number of species in an area Biological Evolution The change in inherited characteristics of a population from generation to generation One of the features that distinguishes life from everything else in the universe Due to natural selection and mutation

Four Processes that Lead to Evolution Mutation (radiation, chemicals, viruses) Natural Selection (most “fit) Migration (over geologic time) Genetic Drift (chance) Each of these four processes leads to changes in gene frequency.

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

Natural Selection 4 Characteristics: Genetic Variability (inheritance of traits) Environmental Variability Differential Reproduction Environmental Influence Species: a group of individuals that reproduce with each other

Natural Selection: DDT Malaria: parasitic microbes Microbes carried by mosquitoes and transferred to people 1957: DDT (mosquitoes) and chloroquine (protozoa) resistance through natural selection must attack completely at outset before natural selection leads to resistance Biotechnology

Migration Two populations of the same species become geographically isolated from each other for a long time (Alaska and Siberia) Can no longer reproduce Two new species evolve from an original species due to isolation Loss of geographic isolation can also lead to a new species (alters gene frequency in new habitat)

Genetic Drift Random changes in the frequency of a gene in a population due to chance May determine which individuals become isolated from larger group (bighorn sheep) Can be a problem for rare or endangered species characteristics that are less adapted to existing environmental conditions may dominate (survival less likely) small size reduces genetic variability thus ability to adapt to future changes

Basic Concepts of Biological Diversity Genetic Diversity: total number of genetic characteristics of a specific species, subspecies or group of species Habitat Diversity: different kinds of habitats in a given unit area Species Diversity: Species Richness: total number of species Species Evenness: relative abundance of species Species Dominance: most abundant species

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

Professions and Places: The Ecological Niche and the Habitat Habitat: where a species lives Ecological Niche: a species profession The reason more species do not die out from competition is that they have developed a niche, and thus avoid competition (adaptive radiation – when a species becomes adapted to a specialized role) Species that require the same resources can coexist by utilizing those resources under different environmental conditions

Species Engage in 3 Basic Interactions 1. Competition 2. Symbiosis 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

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

Predation and Parasitism Predation occurs when an organism (predator) feeds on other live organisms (prey), usually of another species. can increase diversity Parasitism occurs when one organism (parasite) lives on, in, or within another (host) and depends on it for existence but makes no useful contribution to it or may harm it.

Environmental Factors that Influence Diversity Increase Diversity: diverse habitat moderate disturbance small environmental variations high diversity at one trophic level mid-succession evolution Decrease Diversity: environmental stress extreme environment severe limitation in essential resource extreme disturbance exotic species geographic isolation

Ecological Gradient change in the relative abundance of a species over an area tolerance (altitude, pollutants, etc.) physiological tolerance: adjusts to pollutant level genetic tolerance (adaptations): some individuals are more resistant than others; pass resistance to future generations

How Geography and Geology Affect Biological Diversity Latitude In general, greater diversity occurs at lower latitudes Topography Slope Aspect (direction the slope faces) Elevation Nearness to a drainage basin Soil Type Sand Loam Silt

Wallace’s Realms: Biotic Provinces Major biogeographic regions of Earth that are based upon fundamental features of the plants and animals found in those regions; species more likely to be related Taxa: Categories that identify groups of living organisms based upon evolutionary relationships or similarity of characteristics (ex: species, families, orders) Biotic Provinces: A geographical region (realm) inhabited by a characteristic set of taxa, bounded by barriers that prevent the spread of those distinctive kinds of life to other regions.

The main biogeographic realms for animals are based on genetic factors .

The major vegetation realms are also based on genetic factors

Biomes A biome is a kind of ecosystem. Similar environments provide similar opportunities for life and similar constraints. Characterized by a dominant vegetation type Rainforest Grasslands Desserts

Biomes A biome is a kind of ecosystem. Similar environments provide similar opportunities for life and similar constraints. Characterized by a dominant vegetation type Rainforest Grasslands Desserts

Convergent Evolution Divergent Evolution The process by which species evolve in different places of times and, although they have different genetic heritages, develop similar external forms and structures as a result of adaptation to similar environments Ex) shapes of sharks Divergent Evolution Organisms with the same ancestral genetic heritage migrate to different habitats and evolve into species with different external forms and structures, but continue to use the same type of habitats Ex) Ostrich

Convergent

Divergent

Island Biogeography Theory of Island Biogeography Adaptive Radiation: Islands have fewer species than continents The smaller the island, the fewer the species Adaptive Radiation: The process that occurs when a species enters a new habitat that has unoccupied niches and evolves into a group of new species, each adapted to one of these niches. Ecological Island: An area that is biologically isolated so that a species occurring within the area rarely mixes with any other population of the same species (pond, desert oasis, city park)

Biogeography and People Europe and Great Britain climatic change mountain ranges Exotic Species species introduced into a new geographic area

Why Invasive Species Are a Serious Problem Today Ease and speed of long-distance travel Airports Passenger ships Intentional and unintentional International trade in exotic pets