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Chapter 7
Biological Diversity
Biological Diversity
• Biological Diversity
– The variety of lifeforms commonly
expressed as the
number of species in
an area (the genes they
contain and the
ecosystems they live
in)
Biological Evolution
• Biological Evolution
(Charles Darwin)
– The change in inherited
characteristics of a
population from
generation to
generation
• Can result in new
species
•
Four Processes that Lead to
Biological Evolution
•
•
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Mutation
Natural Selection
Migration
Genetic Shift
Mutation
• A chemical change in a DNA molecule
• Affects the expressed characteristics (genotype)
when cells or individual organisms reproduce
Natural Selection
• Organisms whose biological characteristics make them
better able to survive and reproduce (leave more offspring)
• 4 Characteristics that allow/cause NS to occur:
– Genetic Variability May allow an organism to adapt
– Environmental Variability changes to the environment
(seasons)
– Differential Reproduction those organisms best adapted to the
environment will have a better chance to reach reproductive age
– Environmental Influence changes to environment over time
• Species:
– a group of individuals that reproduce with each
other
Migration
• Two population of the
same species become
geographically
isolated from each
other for a long period
of time. New species
evolve from an
original species due to
this isolation
• Ex: land bridge b/w
Alaska and Siberia, when
the bridge was cut off –
new species formed
Genetic Drift
• Changes in the frequency of a gene in a
population due to chance Ex: isolation of
bighorn sheep in mountains due to human
activities. Isolation is in small groups and
therefore a small gene pool. Reduces genetic variability
and therefore the ability to adapt to future changes. AND less adaptive characteristics
may dominate
• Can be a problem for rare or endangered
species
Genetic Drift Example
•
Basic Concepts of Biological
Diversity
• Genetic Diversity total # of genetic characteristics of a specific
species. (Total # of genes)
• Habitat Diversity The different kinds of habitats in a given area
• Species Diversity – Three Qualities :
– Species Richness – total # of species
– Species Evenness – relative abundance of a species
– Species Dominance- the most abundant species
The Number of Species on Earth
• No one knows the exact number
• About 1.4 million – 1.8 million species have
been identified and named
• Insects and plants make up most of these
species
• Number will increase
Why are there so many species??
• If species compete for resources, wouldn’t
the losers die off ??????
• The answer lies in the way
they interact
• Competition, predation, parasitism, mutualism and
commensalism
Ecological Niche and Habitat
• Habitat: where a species lives
• Ecological Niche: The sum of all a species
tolerance ranges, under which they can
survive in an ecosystem.
• The reason more species do not die out
from competition is that they have
developed a niche, and thus avoid
competition
Species Engage in 3 Basic
Interactions
• 1. Competition
• 2. Symbiosis – mutualism & commenselism
• 3. Predation-Parasitism
• Each affect evolution, persistence of a species and
the overall diversity of life
• Organisms have evolved together and therefore
adjusted to one another
• Human interventions upset these adjustments
Competition
• Organisms vie for the
same limited resources
in an environment –
food, nutrients, space,
sunlight
•
The Competitive Exclusion
Principles
• 2 species that have exactly the same
requirements cannot coexist in exactly the
same habitat
• Ex) introduction of the gray squirrel into
Great Britain
Symbiosis
• The relationship between 2
organisms that is beneficial
to both and enhances each
•
organisms chances of
persisting
• Obligate symbionts:
– a symbiotic relationship
between two organisms in
which neither by themselves
can exist without the other
– Ex) stomach of a reindeer
Types of Symbiosis
• Mutualism – Two organisms interact in a
manner that is beneficial to both
• Birds removing ticks from the back of a Rhino
• Bacteria or protozoa living in the gut of an animal
• Commenselism – Two organisms interact
and it benefits one, but has no impact on the
other
• Plants that live on the roots of other plants to obtain
more water
commensalism
•
Parasitism
• One organism gains
•
energy by living on or
inside a host organism.
– Ticks on mammals
– Hookworms inside
mammals
• Parasites are much
smaller than their hosts
and rarely kill them
Predation
• An organism feeds on part or all of another
organism (prey)
– Unique strategies for survival
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Pursuit and ambush
Mimicry
Camouflage
Chemical Warfare (poisons)