Evolution,
Natural
Selection and
Speciation
Genes, Populations, and
Species


Genes are distinct pieces of DNA that
determine the characteristics an individual
displays
A population includes all organisms of the
same kind found in the same region


Populations evolve – individuals do not
A species is a population of all the organisms
potentially capable of reproducing naturally
among themselves and having offspring that
also reproduce
Adaptation
 The
acquisition of traits that allow a
species to survive in its environment
 Types:



Structural
Behavioral
Physiological
Natural Selection



The process of better-selected individuals passing
their traits to the next generation
Survival of the Fittest!
Charles Darwin developed this theory while
studying on the Galapagos Islands

Example: Giraffes

Structural, Behavioral or Physiological?
More resistant Bed Bugs!!

Studies published in January
2011 show that modern bed
bugs are more resistant to
pesticides. New bugs’ have
stronger nervous systems
and they produce enzymes
that can break down
pesticides. Bugs from
decades ago have—which
are kept in isolated labs—
are not nearly as resistant.

Structural, Behavioral, or
Physiological?
More Pitcher
Plants
Whatever their evolutionary
origins, foraging, flying or
crawling insects such as flies are
attracted to the cavity formed
by the cupped leaf, often by
visual lures such as anthocyanin
pigments, and nectar bribes. The
sides of the pitcher are slippery
and may be grooved in such a
way so as to ensure that the
insects cannot climb out. The
small bodies of liquid contained
within the pitcher traps are called
phytotelmata. They drown the
insect, and the body of it is
gradually dissolved.
Conditions of Natural
Selection





Individuals must have genetic variation
More offspring are produced than they need
to replace themselves, most die
Excess number of individuals results in
shortage of resources, which results in
competition
Due to variation, some individuals are better
fit to survive and reproduce
As time passes, percentage of favorable
variations increases and unfavorable
variations decrease
Tolerance Limits
 The
range at which an organism can
survive and reproduce
Selection Pressure
A
wide range of factors applying pressure
on individuals in a population (Ex. pH, light
availability, oxygen Levels, Temp, Salinity
levels)
Lichens are Indicators
 An
indicator is a sign that something isn’t
in balance
 Lichens are indicators of pollution
Evolutionary Patterns
 Speciation
is the production of a
new species from a previously
existing species
 Extinction is the loss of an entire
species
 Coevolution is the concept that two
or more species can influence the
evolutionary direction of the other
 i.e.
grazing animals and grass species
Habitat vs. Ecological Niche
 Habitat–
describes the place or set of
environmental conditions in which a
particular organism lives
 Ecological Niche—describes the role
played by species in a biological
community or the total set of
environmental factors that determine a
species distribution
 Fundamental vs Realized Niche
Fundamental vs Realized
Niche
Competitive Exclusion
Principle
 States
that no two species can occupy
the same ecological niche for long
 The one that is more efficient in using
resources will exclude the other
Rat vs. Panda
We say that the bamboo
is endemic to that area—
not found anywhere else
Resource Partitioning
Species will
coexist—but
utilize different
parts of the
same resource
This can lead to Speciation
 Speciation—development
of a new
species
 ‘Occurs very gradually over immensely
long time’ Darwin
2


mechanisms for Speciation
Geographic Isolation/Allopatric Speciation
Sympatric Speciation
Geographic Isolation or
Allopatric Isolation
 Species
arise in non-overlapping
geographic locations
Sympatric Speciation
 Same
region, different niche leads to
reproductive isolation
Example of Allopatric
Speciation
Isthmus of Panama
Types of Selection
Directional Selection
Examples: Giraffes, Beak Size, Bed bugs, pitcher
plants, mating calls
Types of Selection
Stabilizing Selection
Example: Birth Weight, robin eggs
Types of Selection
Disruptive Selection
Example: Plant Growth at Mining Sites, black
and white peppered moths, bunny rabbits
Taxonomy
 The
study of types of organisms and their
relationship
Binomials
 They
show these relationships
Taxonomy
 Kingdom
 Phylum
 Class
 Order
 Family
 Genus
 Species
Human Taxonomy
 Kingdom
- Animalia
 Phylum - Chordata
 Class – Mammalia
 Order – Primates
 Family – Hominidae
 Genus – Homo
 Species - Homo sapiens
6 “Kingdoms”
 Bacteria
 Archeabacteria
 Fungi
 Protist
 Animal
 Plant
Actually their own domains
now
Competition
 Intraspecific—competition
within a
species
 Interspecific—competition between
species
 Examples?
Predation
 Organisms
that feed on others
 Predation helps keep the food web in
balance
 Examples?
Coevolution
 Organisms
that evolve together over tens
of thousands of years
 Predator—Prey Relationships
 Examples?
Mimicry
 Organisms
trying to mimic other organisms
 This provides advantage!
 Batesian—when
a harmless species
mimics a distasteful/poisonous species
 Mullerian—when two
unpalatale/dangerous species look alike
Mimicry
 Batesian:
 Mullerian:
Symbiosis
Beneficial Relationships
 Mutualism—both

species benefit
Example Videos
 Commensalism—one
unaffected

Example Videos
 Parasitism—one

benefits, the other is
benefits, one suffers 
Example Videos
Keystone Species
 Plays
a critical role in biological
community that is out of proportion to its
abundance.
 The gain or loss of these species ‘ripples
across trophic levels’
 Example:
Steady growing Fig fruit
Primary Productivity
 The
rate of biomass production—an indication of
the rate of solar energy conversion to chemical
energy
Abundance vs. Diversity
 Abundance—the
total number of
organisms in a community
 Diversity—the number of different species,
niches or genetic variation present.
 Compare
Grasslands to the Rain forest
 _________________________________________
_________________________________
Climate History
Equator Areas have higher
primary productivity- this results in
high diversity and lower
abundance of species
Higher Latitudes have lower primary
productivity- this results in lower
diversity but higher abundance of
species
Community Structure varies
based on organisms’ needs
Random—individuals live where resources are
available
Examples: Flowers, Animals
Uniform—individuals live equidistant from each other
to partition resources
Examples: Sagebrush, seabird
nesting space
Clustered—individuals gain advantage by living in
clusters
Examples: Fish, plants, wolves
Edge Effects

A change in species composition, physical
conditions, or other ecological factors at the
boundary between two ecosystems
Examples:
Forest and Grassland
Fresh water and Salt water
Ecotones


Boundaries between adjacent communities
Because resources exist for both ecosystems on the
boundary, higher biodiversity is often observed at
ecotones
In which of the following
relationships does neither
organism benefit?
 Mutualism?
 Commensalism?
 Competition?
 Predation?
 Parasitism?
How are ways a predator
catches its prey?
 Active
vs. Passive
Add this to your notes- Crypis—an
organisms ability to avoid
observation through camouflage
 Aposematism—anticamouflage,
warns
predators through wild colors/patterns
Preserving Habitats
Because of the increase in biodiversity along boundaries, laws
protected boundaries from being hunted. Now we realize that not
only preserving edges is important, but we should preserve large
blocks of land. Many species live in the ‘core’ of communities and
rely on the block as a whole. There are corridors that link blocks
together.
Communities Change Over
Time

Every community starts with its pioneer
species—the first hardy species inhabiting a
land (microbes, mosses and lichens)

Eventually the area reaches climax
community—a relatively stable, long-lasting
community reached in successional series,
usually determined by climate and soil type.
Some ecologist think climax community is
theoretically unreachable because there are
always disturbances.
History shows examples of…

Primary Succession: land that is bare soil—a
sandbar, mudslide, rock face, extreme fire,
volcanic flow--colonized by living organisms
where none lived before

Secondary Succession: an existing community
is disturbed and a new one develops form the
biological legacy of the old
Examples: Abandoned farm fields, minor
forest fire, hurricane
Disturbance
Any force that disrupts the established patterns of
species diversity and abundance.
Examples:
African elephants rip out small trees and trample shrubs
Humans cut down forests to build roads (any humancaused event is referred to as anthropogenic)


Now a days--Ecologists agree that disturbances are
healthy for ecosystems—it gives the underdog
species a chance and sets back the supreme
competitors. This wasn’t always the case—fire and
predator suppression was popular among wildlife
groups for most of the 20th century.
Disturbance-Adapted Species
 Some
species thrive and rely on
disturbance
 Example—Grass in the savannas,
coniferous trees in the forest
 The disturbance sets back their predators
 Nature will always restore balance
Introduced Species
 Can
cause profound community change
 Rats, goats, cats and pigs liberated from
sailing ships onto islands cause drastic
negative affects—there populations grow
quickly and they aren’t a natural part of
the local food webs
 Mongooses were introduced to Hawaii to
control rat populations--FAIL