Biological Communities and Species Interactions

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

determine abundance and distribution 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.

Tolerance Limits

Adaptation Adapt is used in two ways: Limited range of physiological modifications Inheritance of specific genetic traits Evolution Microevolution Macroevolution

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

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

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

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

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

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

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)

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

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

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

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

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

Resource Partitioning Law of Competitive Exclusion Migrate, extinct, or partition

Types of Species Generalist Specialist broad niches tolerate wide range of environmental variations Specialist narrow niches more likely to become endangered do better under consistent environmental conditions

r and k strategists The r-strategists High biotic potential – reproduce very fast Are adapted to live in a variable climate Produce many small, quickly maturing offspring = early reproductive maturity “Opportunistic” organisms The K-strategists Adaptations allow them to maintain population values around the carrying capacity They live long lives Reproduce late Produce few, large, offspring

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

Nonnative/Exotic/Alien Species 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

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

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

Predator Adaptations

Prey Adaptations

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

Symbiosis Symbiosis Mutualism - Both members benefit. Insects and flowers Ex. Yucca plant and moth

Mutualism

Symbiosis Cont… Commensalism Sharks and remora Whales and barnacles

Symbiosis Cont… Parasitism – Humans and Tapeworms

Ecological Processes Primary Succession Secondary Succession Ecological Succession Primary Succession Secondary Succession

No preexisting seed bank 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

Primary Succession Glacier Retreat

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