BIODIVERSITY + EVOLUTION Chapter 4

BRIDGING THE GAP  Biodiversity is all of the differences amongst the living world.  So how do topics already covered in this course relate to biodiversity?  Why is biodiversity important?

SPECIES DIVERSITY  All of the different organisms that exist on Earth  Species abundance: Total # of individuals  Species richness: Total # of species

GENETIC DIVERSITY  Variation of alleles / genes within a gene pool  All of the genes within a population.

ECOSYSTEM DIVERSITY  Differences amongst ecosystems / life zones / biomes  Deserts  Tundra  Rainforests  Praries

FUNCTIONAL DIVERSITY  Differences of biogeochemical processes that exists  Cycling of nutrients and energy transfers

CLOSER LOOK AT EVOLUTION  GENE POOL- all of the possible genes that exist within all the individuals of a single population.  ALLELES- alternate forms of a trait (gene) that are found at a specific location on a specific chromosome.  VARIATIONS- differences among genes or individuals.  Required for natural selection to occur.  Variations are RANDOM  Continuous: differences that can be seen across a spectrum (height, weight, skin color)  Discontinuous: phenotypes fall into distinct types (blood type)  MUTATIONS- any random change in a DNA sequence  Caused by mutagens  Can be silent or deadly  Lead to evolution

TYPES OF EVOLUTION  Microevolution  Evolution on a small scale within a single population.  Change in one gene pool over time  Due to genetic mutations.  Macroevolution  Life history of evolution.  Periods of  Stability  Change  Speciation  Extinction  Due to mutations, gene flow, genetic drift and natural selection  Characterized by:  NEW SPECIES  EXTINCTION OF SPECIES

WHAT IS THE UNDERLYING CAUSE OF BIOLOGICAL EVOLUTION?  Mutations  Inheritable changes in DNA  Natural Selection  Certain traits (genes) are more suitable to a given environment and therefore remain within the gene pool. Evolution by natural selection. A population of bacteria (a) is exposed to an antibiotic, which (b) kills most individuals, but none of those possessing a trait that makes them resistant to the drug (shown in red). The resistant bacteria multiply (c) and eventually, (d) replace all or most of the nonresistant bacteria.

WHAT IS NATURAL SELECTION?  The ability to inherit a trait and pass on that trait.  REQUIRES:  VARIATION  Inheritable traits  reproductively successful individuals  RESULTS IN:  Increase in allele frequency of beneficial allele and a decrease in the nonbeneficial alleles.

DIRECTIONAL SELECTION:  Occurs when natural selection favors one extreme of continuous variation. Over time, the favored extreme will become more common and the other extreme will be less common or lost.  Peppered moth  Antibiotic / Pesticide Resistance

STABILIZING SELECTION  Occurs when selective pressures favor against the two extremes and the average becomes the new norm.  Human birth weight  Short plants can’t compete for resources, tall plants can’t withstand wind so the medium height plants are favored

DIVERSIFYING / DISRUPTIVE SELECTION  Rarest of all types of selections  Environmental factors favor the extremes over the average  Peppered moths

LINK ADAPTATION AND EVOLUTION TO THE FOLLOWING

GEOGRAPHIC ISOLATION  Separation of populations due to physical land features  Over time change in allele frequency of gene pools ultimately leads to new species

COEVOLUTION  Evolutionary adaptations in one species causes related adaptations in another species.  Normally seen in:  Predator-prey interactions  Pollinator – pollinated interactions  acacia and ants acacia and ants

ECOLOGICAL NICHES AND ADAPTATIONS  Niche  Role an organism plays within its ecosystem.  Related to  Range of tolerance to abiotic factors  Type and amount of food or resources consumed  Interactions with organisms  Role it plays in nutrient cycling

TYPES OF NICHES 1. Fundamental - The full potential without any limitations - Doesn’t exist in nature because competition and limited resources - Think competitive exclusion principle. - No two species can occupy the same niche indefinitely 2. Realized  Part occupied based on competition and limitations of resources.

RESOURCE PARTITIONING DUE TO COMPETITIVE EXCLUSION PRINCIPLE… Competitive Exclusion No two species can occupy the same niche indefinitely Resource partitioning Utilizing different areas to limit competition Realized niches

GENERALIST  Huge fundamental niche  Organisms that can live in a wide variety of locations, survive on various food sources and large range of tolerance

SPECIALISTS  Small fundamental niche  Organisms that are uniquely adapted to very stable environments, live on single food source and in one physical location. Have a very narrow range of tolerance.

SO WHAT DETERMINES WHERE WE FIND CERTAIN SPECIES?  Competition  Fighting for resources  Interspecific: Competition between different species  Intraspecific: Competition between members of the same species

SO WHAT DETERMINES WHERE WE FIND CERTAIN SPECIES?  Resource Partitioning  Utilizing resources more efficiently by sectioning off

SO WHAT ELSE DETERMINES WHERE WE FIND CERTAIN SPECIES?  Abiotic Limiting Factors  Sunlight, temperature, precipitation, wind, altitude, fire frequency, soil  Light penetration, water currents, dissolved nutrient concentrations, turbidity, salinity  The Limiting Factor Principle: Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.

RANGE OF TOLERANCE  Range of tolerance: The entire set of environmental factors, such as air temperature or soil moisture, which an organism is potentially able to survive.  The distribution of a species will be controlled by that environmental factor (limiting factor) for which the organism has the narrowest range of tolerance.  Organisms may have a wide range of tolerance for one factor and a narrow range for another.  It only takes ONE physical or chemical variable to limit a species distribution  Organisms that have a wide range of tolerance for limiting factors are likely to be widely distributed

RANGE OF TOLERANCE