Transcript 5-Evolution/Biodiversity

5-Evolution/Biodiversity
Melinda Calderon
5.1
There is overwhelming evidence
for the evolution of life on Earth
Evolution occurs when heritable
characteristics of species change
Happens over successive generations not over night or even
in a lifetime
This happens through mutations and genetic variations
The fossil record provides
evidence for evolution
Fossils are the preserved remains of animals, plants, and other organisms from
the past that shows the gradual change of species over time.
Over time we can see
that the organisms grew a
stronger core and little
limb branches
Selective breeding of domesticated animals
shows that artificial selection can cause
evolution
Selective breeding- breeding plants and animals for specific genetic traits.
Shows a noticeable and organized record of recent changes in genetic characteristics over
a few dozens of generations that man has selected to breed.
For example, chickens that produce more eggs or cows that produce more milk are
selected to breed, so they could pass these advantageous traits onto next generations.
Evolution of homologous structures by adaptive
radiation explains similarities in structure when
there are differences in function
Common internal structures can be similar in diverse
animals that have evolved from a common ancestor.
The standard example of homologous structures is the
“Pentadactyl limb” which is the five digit limb found in
animals such as humans and dolphins Even though
the shape, size and function of this structure vary
between species, the general structure, number and
position of the bones in these limbs are the same.
Populations of a species can gradually
diverge into a separate species by evolution
If two populations of the same species become separated so that they do not
reproduce or interbreed because they become separated by geographical
boundaries Over time, these populations go through a process called speciation
where they change so that they are recognizably different and can or do not
interbreed if they were to merge together again.
Continuous variation across the geographical
range of related population matches the
concept of divergence
Darwin studied how finches adapted to their
surroundings in the Galapagos, as you can see
they are all still pretty similar.
5.2
The diversity of life has evolved
and continues to evolve by
natural selection
Natural selection can only occur if there is
variation among members of the same
species
Throughout a species there is already much genetic variation,
and Individuals with the genes that are best suited for their
environment will survive and reproduce.
If there was no variation within a species, then all individuals
would be the same and no individual would be favoured
over the other and natural selection would not take place
This leaf bug would survive with its genes that allow for
camouflage for the habitat of the leaf it lives near.
Mutation, meiosis and sexual reproduction
cause variation between individuals in a
species
Sexual reproduction allows for combination of
genetic material contributed from both parents.
Meiosis allows for 50% of the female's
chromosomes and 50%of the male’s
genetic mutations might occur where new alleles are
produced. Genetic mutations are the original
source of variation within a species.
Adaptations are characteristics that make an
individuals in a species
Where and how an organism lives is largely due to
its specific adaptations that allow it to survive
and reproduce in a particular area or habitat
In other words, their structure allows them to
function in that environment which adapt
through mutations and natural selection
Polar bears have white hair so the blend in with the
snow but black skin to stay warm
Species tend to produce more offspring than
the environment can support
When parents don’t spend a lot or even any time caring for their young, they
produce many offspring. This is a reproductive method used to make sure some
offspring make it to the next generation. For instance, fish produce thousands of
eggs but only few make it to adulthood. Most mammal parents that put a lot of
time and energy protecting and raising their young tend to have far smaller litters.
Also, they produce to their carrying capacity which prevents the populations from
dying off but also causes competition.
Individuals that are better adapted tend to
survive and produce more offspring while
less well adapted tend to die or produce
fewer offspring
The organisms with the beneficial characteristics will
be able to out-compete the other individuals with the
less beneficial or harmful genetic traits for limited
resources and mates. Again… Natural selection...
Individuals that reproduce pass
on characteristics to their
offspring
Over many generations the accumulation of
these beneficial genetic traits may result
in a change in the population known as
evolution.
Natural selection increases the frequency of
characteristics that make individuals better adapted and
increases the frequency of other characteristics leading
to changes within the species
Since the better adapted individuals
of a species are the ones that
survive, reproduce and pass their
genes on to the next generation,
these alleles will become more
frequent within the population. This
occurs over many populations.
5.3
Species are named and classified
using an internationally agreed
system
The binomial system of names for species is
universal among all biologists and has been
agreed and developed at a series of
congresses
This system is so that all organisms can have
the same name and understanding
internationally. For instance, up north they call
this a crayfish, and down south we call it a
crawfish and it's obviously different in different
cultures, but its scientific name is Cambarellus
diminutus
When species are discovered they
are given scientific names using
the binomial system
The first name in the binomial naming system is
called the genus and is always capitalized.
The second name starts with a small letter and
is called the species
For effective communication
Taxonomists classify species
using a hierarchy of taxa
Scientists arrange or organize species into
a hierarchical set of groups in order to
organize organisms into specific similar
groups based on similar characteristics,
as it goes up the more organisms are in
the group
All organisms are classified into
three domains
The principal taxa for classifying eukaryotes
are kingdom, phylum, class, order, family,
group, species
King Phillip Came Over For Good Soup
Here's an example for humans
In natural classification, the genus and
accompanying higher taxa consist of all the
species that have evolved from one common
ancestral species
Taxonomist sometimes classify groups of
species when new evidence shows that a
previous taxon contains species that have
evolved from different ancestral species
Natural classification helps in identification of
species that allows the prediction of
characteristics shared by species within a
group
very useful for research into biodiversity
A dichotomous key could be used to put an
organism into a classification that fits that
organism the best
Since organism evolved from a common
ancestor, new species would share similar
characteristics (likely internal), allowing for
easier identification and classification.
5.4
Cladistics
A clade is group of organisms
that have evolved from a common
ancestor
Over time species evolve and split
to form new species
Branch points in the tree represent
the time at which the two taxa
split from each other
Evidence for which species are a part of a
clade can be obtained from base sequences
of a gene or corresponding amino acid
sequence of protein
Sequence differences accumulate gradually
so there is a positive correlation between the
number of differences two species and the
time since they diverged from common
ancestor
Pentadactyl limbs show that the
mutations evolve into different
species
Traits can be analogous and
homologous
These are all used for flight
These are all from the
same ancestor
Cladograms are tree diagrams that show the
most probable sequence of divergence in
clades
Evidence from
cladistics has shown
the classifications of
some groups based
based on structure
did not correspond
with the evolutionary
origins of a group of
species