Lecture 3. EVOLUTION, BIOLOGICAL COMMUNITIES, AND SPECIES INTERACTIONS

Adaptation

• One of the most important concepts in biology.
• The acquisition of traits that allow a species to survive in its environment.

Acclimation

• When an individual organism can respond immediately to a
  changing environment.

Genetic traits

• passed from generation to generation and allow a species to
  live more successfully in its environment. This process of adaptation to
  environment is explained by the theory of evolution.

Evolution

• the basic idea is that species change over generations
  because individuals compete for scarce resources.

Natural Selection

• the process of better-selected individuals passing their
  traits to the next generation.

Mutations

• changes to the DNA coding sequence of individuals that
  occurs occasionally, and the changed sequences are inherited by
  offspring.

1. Physiological stress due to inappropriate levels of some critical
   environmental factor, such as moisture, light, temperature, pH, or specific
   nutrients.
2. Competition with other species
3. Predation, including parasitism and disease
4. Luck.

Limiting Factors of Species

Critical Factor

• According to the chemist Justus von Liebig (1840), the single factor in shortest
  supply relative to demand is the critical factor determining where a species lives.
• Temperature, moisture level, nutrient supply, soil and water chemistry, living
  space, and other environmental factors must be at appropriate levels for
  organisms to persist.

Victor Shelford

• Ecologist who (1877-1968) expanded Liebig's principle.
• He stated that each environmental factor has both minimum and maximum
  levels, called tolerance limits, beyond which particular species cannot survive or
  is unable to reproduce.

Tolerance Limits

• The single factor closest to these survival limits is the critical factor that limits
  where a particular organism can live.
• In some species, tolerance limits affect the distribution of young differently than
  they affect adults.

Habitat

• the place or set of environmental conditions in which a particular
  organism lives.

Ecological Niche

• describes both the role played by a species in a biological
  community and the set of environmental factors that determine its distribution.

Charles Elton

• British Ecologist who defined the concept of niche in

1. According to him, each species had a role in a community of species, and
   the niche defined its way of obtaining food, the relationships it had with other
   species, and the services it provided to its community.

G. E. Hutchinson

• The American limnologist who, thirty years later,
  proposed a more biophysical definition of niche. According to him, every
  species exists within a range of physical and chemical conditions such as
  temperature, light levels, acidity, humidity, or salinity. It also exists within a set of biological interactions such as predators and prey present, defenses, or nutritional resources available.

Generalists

• species that tolerate a wide range of conditions or exploit a wide
  range of resources. Example: Species that thrive in broad variety of environments
  such as weedy species or pests (rats, cockroaches, or dandelions).

Specialists

• species that have a narrow ecological niche. Examples are Giant
  Panda and Giant Saguaro.

Speciation

o The development of a new species.
o As a population becomes more adapted to its ecological niche, it may
develop specialized or distinctive traits that eventually differentiate it
entirely from its biological cousins.

Allopatric Speciation

• speciation that occurs when populations are
  geographically separated.

Geographic Isolation

• when the habitat are far enough apart that
  population were genetically isolated; they couldn't interbreed with
  populations on the other habitat.

Sympatric Speciation

• speciation that occurs within one geographic
  area.

Behavioral Isolation

• when two identical species live in similar habitats
  but have different mating calls. This difference is enough to prevent
  interbreeding.

Directional Selection

• the shift toward one extreme of a trait.

Taxonomy

• The study of types of organisms and their relationships.
• With this, organisms can be traced which common ancestors they have
  descended.

Binomials

o also called Scientific or Latin Name
o Identify and describe species using Latin or Latinized nouns and adjectives, or names of people or places.
o Scientists communicate using scientific names instead of common names like lion, dandelion, or ant to avoid confusion.

Species Interactions

• Competition leads to resource allocation.
• Predation is an important type of selective pressure.
• Symbiosis benefits both species involved.

Competition

• A type of antagonistic relationship within a biological community.
• Organisms compete for resources that are in limited supply such as energy and
  matter in usable forms, living space, and specific sites to carry out life's activities.
• Competition shapes a species population and biological community by causing
  individuals and species to shift their focus from one segment of a resource type
  to another.

Intraspecific competition

• competition among members of the same
  species.

Interspecific competition

• competition between members of different
  species.

Predator

• Any organism that feeds directly on another living organism, whether or not this
  kills the prey.
• Herbivores, carnivores, and omnivores, which feed on live prey, are predators.
• Predation is a powerful but complex influence on species populations in
  communities.

Effects of Predator

1. All stages in the life cycles of predator and prey species.
2. Many specialized food-obtaining mechanisms.
3. The evolutionary adjustments in behavior and body characteristics that
   help prey avoid being eaten and help predators more efficiently catch
   their prey.

Symbiosis

• Two or more species live intimately together, with their fates linked.
• Symbiotic relationships often enhance the survival of one or both partners.

Mutualism

• type of symbiosis in which both members' benefits. (e.g. Dogs and Humans)

Commensalism

• type of symbiosis in which one member clearly benefits
  and the other apparently is neither benefited nor harmed. (e.g. a spider building a web on a tree)

Parasitism

• a form predation may also be considered symbiosis because
  of the dependency of the parasite on its host. (fleas and mosquitoes feed
  on blood from other organisms

Endosymbiosis

• one species living inside another one. (e.g. Protozoans
  that live inside termites and help them digest wood)

Ectosymbiosis

• one species living on the surface of the other species.
  (e.g. Lice that feed on the skin, blood, or oil secretions of the host)

Keystone Species

• Plays a critical role in a biological community that is out of proportion to its
  abundance.
• Thought to be the top predators like lions, wolves, and tigers that limited
  herbivore abundance and reduced the herbivory of plants.
• Scientists now recognize that less-conspicuous species also play keystone roles.

Community Properties

• Productivity is a measure of biological activity.
• Abundance and diversity measure the number and variety of organisms.
• Resilience and stability make communities resistant to disturbance.

Primary Productivity

• The rate of biomass production.
• An indication of the rate of solar energy conversion to chemical energy.
• The energy left after respiration is net primary production.

Abundance

is an expression of the total number of organisms in a biological community.

Diversity

is a measure of the number of different species, ecological niches, or
genetic variation present.

Abundance and Diversity

• The abundance of a particular species often is inversely related to the total
  diversity of the community.
• Communities with a very large number of species often have only a few
  members of any given species in a particular area.
• Diversity decreases but abundance within species increases as we go from the
  equator toward the poles.

Ecological structure

refers to patterns of spatial distribution of individuals and
populations within a community, as well as the relation of a particular community
to its surroundings.

Resilience and Stability

• Many biological communities tend to remain relatively stable and constant over
  time.

Robert MacArthur

• a graduate student at Yale, proposed that the more
  complex and interconnected a community is, the more stable and resilient it will
  be in the face of disturbance.

Three kinds of stability or resiliency in ecosystems

1. Constancy - lack of fluctuations in composition or functions
2. Inertia - resistance to perturbations
3. Renewal - ability to repair damage after disturbance

edge effects

The boundary between one habitat and
its neighbors is an important aspect of
community structure.

Ecotones

are what the ecologists call the boundaries between adjacent
communities.

Closed Community

• a community that is sharply divided from its neighbors.

Open Community

• a community with gradual or indistinct boundaries over
  which many species cross.

Climax Community

is the community that developed last and lasted the longest.

Ecological Succession

is the history of community development. When a
succession occurs, organisms occupy a site and change the environmental
conditions.

Primary succession

• Land that is bare of soil (a sandbar, mudslide, rock face,
  and volcanic flow) is colonized by living organisms where none lived before.

Secondary succession

• When an existing community is disturbed, a new one
  develops from the biological legacy of the old.

Ecological development or facilitation

• In both kinds of succession, when
  organisms change the environment by modifying soil, light levels, food supplies,
  and microclimate, the change permits new species to colonize and eventually
  replace the previous species.

Pioneer species

• In primary succession on land, the first colonists (microbes,
  mosses, and lichens) that can withstand a harsh environment with few resources.

Disturbance

-Any force that disrupts the established patterns of species diversity and abundance, community structure, or community properties.
-landslides, mudslides, hailstorms, earthquakes, hurricanes,
tornadoes, tidal waves, wildfires, and volcanoes. Animals can cause disturbance too.

Disturbance-adapted species

• species that can survive periodic disturbance
  (survive fires underground, or resist the flames, and then reseed quickly after
  fires).

Introduced Species

• Continuous introduction of new community members and the disappearance of previously existing species are requirements of succession.
  -New species can be introduced after a stable community already has become established.