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Lecture -7:
Biological Diversity and
Biogeography
ENV 107: Introduction to Environmental Science
Dr. A.K.M. Saiful Islam
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Biological Evolution
† Refers to the change in inherited
characteristics of a population from
generation to generation.
† Along with self-reproduction, biological
evolution is one of the features that
distinguish life from everything else in the
universe.
† Biological evolution is a one-way process.
One species extinct, it is gone forever.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
7.2 Process that lead to Evolution:
1. Mutation
† Genes contained chromosomes within cells, are
inherited from one generation to the next.
† Genes are made up of complex chemical compound
called deoxyribonucleic acid (DNA), which made up
of chemical building blocks that form a code, or kind
of alphabetic information.
† External agents such as radiation or certain toxic
organic chemicals, comes in contact with DNA and
alters it.
„ When DNA changes, it is said to have undergone
mutation.
† It can result in a new species whether or not that
species is better adapted than its parental species to
the environment.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
2. Natural Selection
„ Natural selection is a process by which organisms
whose biological characteristics better fit them to the
environment are better represented by descendants
in future generations than are those whose
characteristics are less fit for the environment.
„ Figure 72. Dark variation of birds are dominant in
polluted urban areas and light natural coloration of
bird in rural region illustrates the features of
biological evaluation (natural selection) due
industrial mechanism.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Industrial Melanism and Natural
Selection
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
3. Migration
„ The migration of one population of a species into
a habitant previously occupied by another
population is a process that lead to change in
gene frequency.
„ Even organisms that do not move themselves
may have reproductive structures that migrate.
For example, seeds of flowering plants for
example are blown by the wind and moved by
animals.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
4. Genetic Drift
„ Refers to changes in the frequency of a gene in a
population as a result of chance rather than
mutation, selection or migration.
„ Chance may determine which individuals become
isolated in a small group from a larger population and
thus which genetic characteristics are most common
in that isolated population.
„ The individuals may be better, poorly or neutrally
adapted to the environment.
† For example bighorn sheep live in the mountains of the
desert southwest of US.
† Before human settlement, they can migrate and move
freely.
† With human settlement on that region, many population
of bighorn sheep have become isolated and that cause
problem to their survival.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Biological Diversity
† Biological Diversity involves three concepts:
„ Genetic diversity: the total number of genetic
characteristics, sometimes of a specific species,
subspecies, or group of species.
„ Habitat diversity: the diversity of habitats in a
given unit area.
„ Species diversity: which has three aspects:
† Species richness – the total number of species
† Species evenness – the relative abundance of
species
† Species dominance – the most abundant species
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Terms related to Species Habitat
† Exotic species: - a species introduced into new
geographic area.
† Endemic Species: - a species that is native to a
particular area and not native elsewhere is called an
endemic species.
„
For example, Monterey pine is endemic to a portion of the
California coast and exotic in New Zealand.
† Cosmopolitan species: - a species with a broad
distribution, occurring all over the world wherever the
environment is appropriate.
„
For example, the moose is found in both North America
and Europe and is therefore a cosmopolitan.
† Ubiquitous Species: - species that are found almost
anywhere.
„
For example, human are ubiquitous as are some bacteria.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Interactions between species
† There are three basic kinds of
interactions between species
„ Competition – in which the outcome is
negative for both groups.
„ Symbiosis – which benefits both
participants
„ Predation-parasitism – in which the
outcome benefits one and is detrimental
to the others.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Competitive exclusion: Squirrel
(a) American gray squirrel
(b) European red squirrel
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Competitive exclusion of flour
beetle
†
†
†
A: Likes warm, dry condition
B: Likes cool, wet condition
Both: Like to eat wheat
In uniform environment, one will
Win out over other
In a mixed environment, the
Beetles will use separate parts
Of the habitat
In either case, beetles do not
coexists
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Results under warm dry condition
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Reindeer
and
Symbiotic
Bacteria
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Environmenatal factors that
influence diversity
† A. Factors that tend to increase diversity
1. A physically diverse habitant
2. Moderate amounts of disturbance (such as fire
or storm)
3. A small variation in environmental condition
(temperature, precipitation etc)
4. High diversity at one trophic level increase the
diversity at another trophic level
5. An environmental highly modified by life (for
example a rich organic soil).
6. Middle stages of succession.
7. Evolution.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
Environmenatal factors (cont..)
† B. Factors that tend to decrease diversity
1. Environmental stress.
2. Extreme environments (conditions near to limit
of what living things can withstand).
3. A severe limitations in the supply of an essential
resources.
4. Extreme amount of disturbance.
5. Recent introduction of exotic species (species
from other area).
6. Geographic isolation.
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam
ENV 107:Introduction to Environmental Science © Dr. Akm Saiful Islam