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Biological Communities and Species Interactions 1 Why is Earth "just right" for life? • Distance from sun • Size • Rotation • Orbit around sun • Atmospheric evolution © Brooks/Cole Publishing Company / ITP 2 Who lives where and why? • • Interaction of several factors determines biogeographical distribution. determine abundance and distribution Species requirements and tolerances can also be used as useful indicators. 3 Tolerance Limits 4 Adaptation • Adapt is used in two ways: Limited range of physiological modifications Inheritance of specific genetic traits allowing a species to live in a particular environment. Evolution Microevolution Macroevolution 5 Evolution & Adaptation • Microevolution- change in gene frequency within a population • Macroevolution- formation of new species from ancestral species © Brooks/Cole Publishing Company / ITP Genes mutateindividuals selectedpopulations evolve 6 Microevolution Four processes drive microevolution: 1. Genetic variability 2. Natural selection © Brooks/Cole Publishing Company / ITP 7 Microevolution Four processes drive microevolution, cont: 3. Gene flow 4. Genetic drift: 8 Natural Selection Directional selection favors individuals with traits that are at one end of a distribution • giraffe example • "It pays to be different.” © Brooks/Cole Publishing Company / ITP 9 10 Natural Selection Stabilizing selection eliminates individuals at both ends in the spectrum of variation • the average remains the same. • "It pays to be average.” •Ex. Plant height © Brooks/Cole Publishing Company / ITP 11 12 Natural Selection Disruptive (diversifying) selection eliminates average individuals, but favors individuals at either extreme of the spectrum of variation. "It doesn't pay to be normal.“ © Brooks/Cole Publishing Company / ITP 13 14 Convergent Evolution Species from different evolutionary branches may come to resemble one another if they live in very similar environments Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert) 15 16 Coevolution • 1. 2. Evolutionary change Competitive relationships lead to coevolution. Example: Cheetah and gazelle Insects and flowers 17 Macroevolution Speciation-Evolution of a new species-geographical isolation or selective pressure can create an entirely new species. 18 Speciation Geographic isolation can lead to reproductive isolation, divergence and speciation. © Brooks/Cole Publishing Company / ITP 19 Community Relationships • • Habitat Niche Includes: range of tolerance for various physical conditions (temp and water) types and amounts of resources it uses interactions with abiotic and biotic components the role it plays 20 Niche Fundamental niche: theoreticaly use if there were no competition Realized niche: actually uses 21 Resource Partitioning • Law of Competitive Exclusion One will either migrate, become extinct, or partition the resource 22 Types of Species • Generalist broad niches tolerate wide range of environmental variations • Specialist narrow niches more likely to become endangered do better under consistent environmental conditions 23 r and k strategists The r-strategists 1. High biotic potential – reproduce very fast 2. Are adapted to live in a variable climate 3. Produce many small, quickly maturing offspring = early reproductive maturity 4. “Opportunistic” organisms The K-strategists 1. Adaptations allow them to maintain population values around the carrying capacity 2. They live long lives 3. Reproduce late 4. Produce few, large, offspring 24 What Different Roles Do Various Species Play in Ecosystems? • • • • Native Nonnative Indicator species Keystone species 25 Non-native Species • Nonnative/Exotic/Alien Species - Examples: Zebra Mussels in the Great Lakes, Snakehead fish in MD, Mongoose in Hawaii, Cane Toads in Australia 26 Keystone Species Strong interactions with other species which affect the health and survival of those species If a keystone species is removed from a system - the species it supported will also disappear - other dependent species will also disappear 27 SPECIES INTERACTIONS • Predator - Reduce competition, population overgrowth, and stimulate natural selection. o Coevolution 28 Predator Adaptations 29 Prey Adaptations 30 Competition • • Interspecific -different species Results in: migration, population declines Intraspecific - same species Intense due to direct competition for same resources - Territoriality Disadvantages? 31 Symbiosis • Symbiosis Mutualism - Both members benefit. - Insects and flowers Ex. Yucca plant and moth Yucca’s only pollinator is the yucca moth. Hence entirely dependent on it for dispersal. Yucca moth caterpillar’s only food is yucca seeds. Yucca moth lives in yucca and receives shelter from plant. 32 Mutualism 33 Symbiosis Cont… Commensalism - Sharks and remora - Whales and barnacles 34 Symbiosis Cont… Parasitism – Humans and Tapeworms 35 Ecological Processes • Ecological Succession •Primary Succession •Secondary Succession 36 Primary Succession • Gradual establishment of biotic communities in an area where no life existed before • No preexisting seed bank •newly formed islands (i.e. volcanic origin) •retreat of a glacier 37 38 Primary Succession Glacier Retreat 39 Secondary Succession • Gradual reestablishment of biotic communities in an area where one was previously present. • Preexisting seed bank •"old field succession" •forest fire 40 41 42