1 Biological Communities and Species Interactions

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.  Environmental indicators

3 Tolerance Limits

4 Adaptation Adapt is used in two ways:  Limited range of physiological modifications available to organisms.  Inheritance of specific genetic traits allowing a species to live in a particular environment.  Explained by evolution

5 Four causes of evolutionary change: 1.Mutation: fundamental origin of all genetic (DNA) change. Point mutation …some at base-pair level Crossing-over others at chromosome level

6 Four Causes of Evolutionary Change 2.Genetic Drift: populations accumulate different mutations over time. Local spreading of alleles

7 But in discontinuous populations, gene flow is blocked.

8 Four Causes of Evolutionary Change 3. Founder Effect: New population formed, genetic composition depends largely on the gene frequencies within the group of first settlers.

9 Four Causes of Evolutionary Change Individuals with favorable traits are more likely to leave more offspring better suited for their environment 4. Natural Selection -Individuals with favorable traits are more likely to leave more offspring better suited for their environment  Acts on pre-existing genetic diversity.  Limited resources place selective pressures on a population.

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

11 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)

12

13 Coevolution Evolutionary change Evolutionary change  One species acts as a selective force on a second species  Inducing adaptations that act as selective force on the first species Example: Example: 1. Cheetah and gazelle 2. Insects and flowers

14 Community Relationships Habitat – location of species (it’s address) Niche – the species’ occupation  Includes:  range of tolerance for various physical conditions (temp and water)  types and amounts of resources (food, nutrients, space) it uses  interactions with nonliving and living components  the role it plays in the energy flow and matter cycling

15 Niche Realized niche: Realized niche: Resources or habitat a species actually uses. Fundamental niche: Fundamental niche: Full range of resources or habitat a species could live if there were no competition

16 Types of Species Generalist  large niches  tolerate wide range of environmental variations  do better during changing environmental conditions Specialist  narrow niches  more likely to become endangered  do better under consistent environmental conditions

17 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

18 Resource Partitioning Law of Competitive Exclusion - No two species will occupy the same niche and compete for exactly the same resources for a long time period  One will either migrate, become extinct, or partition the resource

19 Resource Partitioning

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

21 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 Examples  top carnivores that keep prey in check  large herbivores that shape the habitat in which other species live  important plants that support particular insect species that are prey for birds  bats that disperse the seeds of plants

22 Non-native Species Nonnative/Exotic/Alien Species – species that migrate into an ecosystem or are deliberately or accidentally introduced into an ecosystem by humans - Examples: West African Killer Bees in Brazil, Mongoose in Hawaii, Cane Toads in Australia

23 SPECIES INTERACTIONS Predator  Prey most successfully on slowest, weakest, least fit members of target population. - Reduce competition, population overgrowth, and stimulate natural selection. o Coevolution

24 Predator Adaptations

25 Prey Adaptations

26 Competition Interspecific -different species for limited resources  Results in: migration, population declines Intraspecific - same species for limited resources  Intense due to direct competition for same resources - Territoriality - defend specific area containing resources  By marking or patrolling  Disadvantages: takes energy, exclusion of male members in terms of breeding

27 Symbiosis Symbiosis - Intimate living together of members of two or more species.  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.

28 Symbiosis Cont…  Commensalism - One member benefits while other is neither benefited nor harmed. - Sharks and remora

29 Symbiosis Cont…  Parasitism –draw resources from host without killing the host (at least in the short term). - Gradually weakens host; may be fatal  Humans and Tapeworms

30 Community Structure Species diversity or richness: the number of different species Species abundance: the number of individuals of each species Diversity decreases and abundance within species increases when moving from the equator to the poles.

31 Ecological Processes Ecological Succession- gradual changing environment in favor of new / different species / communities Primary Succession Secondary Succession

32 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

33

34 Primary Succession Glacier Retreat

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

36

37

38 Disturbance Event that disrupts an ecosystem or community; Natural disturbance tree falls, fires, hurricanes, tornadoes, droughts, & floods Human–caused disturbance deforestation, erosion, overgrazing, plowing, pollution,mining