Biodiversity and Classification
Biodiversity
• Biological diversity is usually the sign of a
healthy ecosystem.
• The greater the diversity of organisms with
in an ecosystem, the greater is the chance
that some of those organisms will be able
to survive change.
Biodiversity
•
There are two levels of biological
diversity:
1. Genetic diversity, which describes the variety of
genes that code for different traits in a given
species
2. Species diversity, which describes the number of
different species.
Classification
• It is often difficult to determine if subtle
physical differences are variation within a
species or variation between different
species of closely related organisms.
• Therefore, scientists need a classification
system to help them study ecological
diversity.
Taxonomic Systems
• Taxonomy – the science of classification
according to the inferred relation ships
among organisms
Taxonomic Systems
•
Biological classification systems have
two main purposes:
1. Identifying organisms
2. Providing a basis for recognizing natural
groupings of living things.
Taxonomic Systems
• Carl Linnaeus (1707-1778)
• Developed a system of
classification based on an
organism’s physical and
structural features, and
operated on the idea that the
more features organisms
have in common, the closer
their relationship.
Taxonomic Systems
• Carl Linnaeus (1707-1778)
• He was the first to use:
• Binomial nomenclature a method of
naming organisms by using two names –
the genus name and the species name.
Taxonomic Systems
• Scientific name is often based on some
characteristic such as colour or habitat:
• Example
– Castor canadensis
• Caster meaning beaver and canadensis meaning
from Canada
• The first part of any scientific name is
called the genus. The second part is
called the species.
Taxonomic Systems
• The two-name system provides an added
advantage by indicating similarities in
anatomy, embryology, and evolutionary
ancestry.
Taxonomic Systems
•
Present classification system there are
seven main levels or taxa.
1.
2.
3.
4.
5.
6.
7.
Kingdom
Phylum
Class
Order
Family
Genus
species
• Today most scientists believe that
organisms have changed over time. The
history of the evolution of organism is
called phylogeny.
• Relationships are often shown in a type of
diagram called a phylogenetic tree.
Assignment
• Read pages 134-139
• Do questions 1-7 on page 139
• Investigation pg 162
Evidence of a Changing Earth
• Evidence of evolution comes from many
lines of investigation.
• Some from direct observation and some
more indirect.
• Evidence gathered from:
– Direct Evidence:
– Fossils
– Radiometric dating
– Indirect Evidence
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Comparative Anatomy
Homologous structures
Analogous structures
Embryology
Vestigial Organs
Physiology
Behaviour
Plant and animal breeding
Biochemistry and genetics
The geographic distribution of species
Evidence from Fossils
• Paleontology – The study of fossils
• Fossilized remains, impressions, and
traces of organisms from past geological
ages provide scientists with direct physical
evidence of past life.
Evidence from Fossils
•
Patterns found in fossils:
1. Different species lived on Earth at various
time in the past.
2. The complexity of living organisms generally
increases from the most distant past to the
present.
3. Living species and their most closely
matching fossils are typically located in the
same geographic region.
Fossilization occurs in many ways
 Organic components of the
organism are replaced by minerals.
 Impressions left by organisms are
preserved by the solidification of
mud.
 Organisms can sometimes be
caught in amber and preserved
– Mammoths, bison and other extinct
mammals have been found frozen
in Arctic ice.
– Acidic Bogs-conditions retard
decomposition
Do you have a date??
 Radiometric dating
 use the radioactive decay
of certain elements to
determine the age fossils
– Example: Carbon-14
Evidence From Biogeography
• Biogeography explores the variation and
distribution of live over the Earth’s surface,
both today and the past.
• Earth’s landmasses have undergone
dramatic changes by the process of
continental drift.
pic
Evidence From Biogeography
• Evidence from biogeography suggest that
different species evolved independently in
isolated parts of the world.
Evidence of Evolution from Biology
• A comparison of the physical anatomy and
genetic makeup of organisms also
provides evidence.
Evidence from Anatomy
• Comparative Anatomy
– Homologous structures
 Structures having similar genetic origin but
different uses in different species.
• Adaptive radiation: The pentadactyl limb has
evolved to suit many niches: digging, running,
flying, swimming, etc.
Ex: Flipper of dolphin and a forelimb of dog
suggests a common ancestor
Indirect Evidence For Evolution
• Analogous structures
 Structures which are similar in
function and appearance but
came from different ancestors.
 Examples: wing of an insect
and a bird
– Good indicators that these
organisms did not evolve from
a common ancestor
– Illustrates convergent evolution
• development of similar forms from
unrelated species due to
adaptation to similar environment
More Indirect
Evidence for Evolution
– Embryology
 The study of organisms in their early stages
of development.
 Closely related organisms go through similar
stages in their embryonic development
 similarities in embryos suggests these
organisms have an evolutionary relationship.
Embryology
Embryology
– Vestigial Organs
• Structure with no known function in present
• Examples: coccyx and appendix in
humans, vestigial leg bones in snakes
Evidence from Biochemistry
• Evidence of evolution has also been found
by comparing biochemical characteristics
of different species.
• Biochemical Evidence
– Analysis of chemicals can be used to show
evolution
– DNA and cytochrome enzyme C (respiration)
are similar in all organisms
– DNA analysis-used determine how closely
related organisms are
 suggest a common ancestor
Assignment
• Read pages 140-148
• Do questions 1 & 2 on page 143 and
question 3 on pg 149
Lamarck and Darwin
Source of Variation:
 Inherited: Determined by the DNA
(genetic material) inherited from the parent
 i.e. hair, eye and skin color
 Acquired: Developed over life time.
 i.e. basketball skills, musical ability
History of Evolution
Lamarck’ Theory
• Lamarck believed that new species were
continually being created by spontaneous
generation
– Spontaneous generation – the belief that
living things arose from non-living matter.
Lamarck’ Theory
• Theory of Use and Disuse: Use-remains strong.
Disuse-weakens and disappears. For example
snakes legs.
– USE Each body part possesses a “will”
which allows it to change in order to better fit
its environment.
• Eg. Short necked giraffe stretches its neck to reach
tree tops and it develops a longer neck
– DISUSE
If a body part is not used it will
begin to disappear
• Eg. Nocturnal animals (ie. Bats) lose their vision
Lemarck’ Theory
• Theory of Acquired Traits: Traits acquired
in life time could be passed on to offspring.
Inheritance of acquired characteristics
Problems with Lamark’s theory
• “Use and Disuse” implies an organism can
sense its needs and physically change to
meet those needs.
• Acquired characteristics are not inherited
• Never confirmed by experimentation.
Darwin’s Theory of Evolution
1. Overproduction
2. Variation.
3. Competition
4. Survival of the
fittest
5. Passing on of successful
traits (speciation)
Overproduction
• Overproduction means that the number of
offspring produced by a species is greater than
the number that can survive.
Variation
• Differences among traits occur among
members of the same species.
• No two individuals are exactly alike
• Caused by:
– Mutation
– Sexual Reproduction
Struggle for existence
• Competition
• Organisms of the same species, as well as
those of different species, must compete for
limited resources such as food, water, and a
place
• Natural selection: Nature selects the organisms
that survive
Survival of the Fittest-Natural
Selection
• The most fit individuals survive
• Fittest means that the individuals are best
suited to the environment
Origin of new species
(speciation)
• Successful individuals reproduce and pass
on their traits
• Over numerous generations, new species
arise by the accumulation of inherited
variation
• When a type is produced that is
significantly different from the original, it
becomes a new species.
Comparison of
Lamarck and Darwin
Darwin
• Organism vary
regardless of the
environment
• The environment then
determines whether a
variation is harmful
(die) or helpful
(survive)
Lamarck
• Individuals change to
suit their environment
• Change is based on
the need or “want” to
change
Sources of Inherited Variation
•
Variability in a species may arise from
two biological processes:
1. Mutations
2. Sexual reproduction
Mutations
• DNA, the hereditary material, is found in
the chromosomes of a cell.
• Genes are segments of DNA that code for
Specific traits.
• Mutation - a random change in the DNA
sequence in a chromosome.
Mutations
•
Mutations can by caused by:
1. Environmental factors
– Chemicals
– Radiation
2. Errors that arise when cells replicate
Mutations
• Mutations are rare in individuals.
• Neutral mutation – a mutation that has no
effect on the organism
• Harmful mutation – a mutation that
reduces an organism’s fitness
• Beneficial mutation – a mutation that
enhances an organisms’ fitness.
Mutations
• Summary:
– Mutations occur at random, with harmful
mutations being more common than beneficial
mutations.
– Harmful mutations are selected against and
therefore do not accumulate over generations.
– Although beneficial mutations are rare, they
are selected for and may accumulate over the
generations.
Sexual reproduction and Variability
• Asexual reproduction – production of
offspring from a single parent: offspring
inherit the genes of that parent only.
– All offspring are identical to parents.
Sexual reproduction and Variability
• Sexual reproduction – the production of
offspring by union of sex cells from two
different parents.
– Offspring are never identical to the parents or
to other siblings.
•
Why are sexually-reproducing species so
variable? There are three reasons.
1. Sexually-reproducing species have two
copies of each gene. One from each parent.
2. The assortment of genes that an offspring
inherits from either parent is determined
randomly.
3. Sexually reproducing species choose
different mates.
Speciation and Evolution
 Species
 A group of similar organisms which share
a common gene pool
 Organisms of the same species normally
interbreed in nature and are capable of
producing fertile offspring
• Population:
– A group of individuals of the same
species occupying a given area at a
certain time
Speciation
•
Speciation – the formation of new
species.
• Most new species are believed to arise
by a three-step process called allopatric
speciation.
1. A physical barrier separates a single
interbreeding population into two or more
groups that are isolated from each other.
Speciation
2. Natural selection works on the separated
groups independently, resulting in
inherited differences in the two
populations. (defenses in selective
pressures).
3. Physical and behavioral differences
accumulate can no longer be sexually
compatible.
• New species evolve from a common ancestor in
response to a new environment
• Eg. From a common finch with a mid-sized beak
the following finches evolved
• Finch with a long beak for poking wood
• Finch with a short, hard beak for cracking seeds
• Finch with a long beak for drinking nectar
Rate of Evolution
•
•
Theory of gradualism – the idea that speciation
takes place slowly.
Theory of punctuated equilibrium- the idea that
species evolve rapidly followed by a period of
little or no change. This theory has three main
assertions:
1. Many species evolve very rapidly in evolutionary
time
2. Speciation usually occurs in small isolated
populations
3. After an initial burst of evolution, species are well
adapted to their environment and do not need to
change significantly for a long period.
Methods of speciation:
• Transformation of one species into
another
• Branching evolution: one or more species
branch off a parent species which
continues to exist.
Divergent evolution – evolution into many
different species.
Adaptation and Change
• Convergent Evolution
– the development of
similar forms from
unrelated species due to
adaptation to similar
environments.
– Ex: the torpedo shape of
dolphins and sharks.
Over time, the two began
to look more and more
alike.