1 Biological Communities and Species Interactions

2 Why is Earth "just right" for life ? © Brooks/Cole Publishing Company / ITP Distance from sun Size Rotation Orbit around sun Atmospheric evolution

3 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.

4 Tolerance Limits

5 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

6 Evolution & Adaptation © Brooks/Cole Publishing Company / ITP Microevolution- change in gene frequency within a population Macroevolution- formation of new species from ancestral species Genes mutate  individuals selected  populations evolve

7Microevolution © Brooks/Cole Publishing Company / ITP Four processes drive microevolution: 1.Genetic variability 2.Natural selection

8 Microevolution 3. Gene flow 4. Genetic drift: Four processes drive microevolution, cont:

9 Natural Selection © Brooks/Cole Publishing Company / ITP Directional selection favors individuals with traits that are at one end of a distribution giraffe example "It pays to be different.”

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11 Natural Selection © Brooks/Cole Publishing Company / ITP 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

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13 Natural Selection © Brooks/Cole Publishing Company / ITP Disruptive (diversifying) selection eliminates average individuals, but favors individuals at either extreme of the spectrum of variation. "It doesn't pay to be normal.“

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15 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) Horned Viper (Middle East Desert)

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17 Coevolution Evolutionary change Evolutionary change  Competitive relationships lead to coevolution. Example: Example: 1. Cheetah and gazelle 2. Insects and flowers

18 Macroevolution Speciation-Evolution of a new species- Speciation-Evolution of a new species-geographical isolation or selective pressure can create an entirely new species.

19 Speciation © Brooks/Cole Publishing Company / ITP Geographic isolation can lead to reproductive isolation, divergence and speciation.

20 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

21 Niche Realized niche: Realized niche: actually uses Fundamental niche: Fundamental niche: theoreticaly use if there were no competition

22 Resource Partitioning Law of Competitive Exclusion  One will either migrate, become extinct, or partition the resource

23 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

24 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 r and k strategists

25 What Different Roles Do Various Species Play in Ecosystems? Native Nonnative Indicator species species Keystone species

26 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

27 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

28 SPECIES INTERACTIONS Predator - Reduce competition, population overgrowth, and stimulate natural selection. o Coevolution

29 Predator Adaptations

30 Prey Adaptations

31 Competition Interspecific -different species  Results in: migration, population declines Intraspecific - same species  Intense due to direct competition for same resources - Territoriality  Disadvantages?

32 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.

33 Mutualism

34 Symbiosis Cont…  Commensalism - Sharks and remora - Whales and barnacles

35 Symbiosis Cont…  Parasitism –  Humans and Tapeworms

36 Ecological Processes Ecological Succession Primary Succession Secondary Succession

37 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

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39 Primary Succession Glacier Retreat

40 Secondary Succession Gradual reestablishment of biotic communities in an area where one was previously present. Preexisting seed bank "old field succession" forest fire

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