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Lecture 1

BIOL 1215 Lecture Notes - Lecture 1: Hornwort, Euglena, Intron

Course Code
BIOL 1215
Anoush Dadgar

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Biology 1215
Species and Speciation
Speciation = creating a new species
Around 10-100 million species on Earth
oEvolution makes it hard to pinpoint a #
oWe don’t know about species deep in ocean, amazons/dense rainforest,
and microscopic organisms
We have identified 1.8 mill species
oThey have a name and we know SOMETHING about them, may just be
appearance etc
There are 3 ways to define species:
oBiological Species Concept
The organism is able to sexually reproduce with each other in
The offspring must be fertile
Orangotangs are physically dif. (look different on dif islands)
and the only way to know if they’re the same species is to
see if they can reproduce in nature
If they are physically different but able to sexually reproduce,
they are different subspecies
Have to wait for animals to sexually reproduce, then have to
wait and see if offspring is fertile (time consuming)
Must be tested in nature
Unable to define asexually reproducing organisms
Extinct species are hard to define
Hybrids (ligers)
oThey do not stop growing
oAre only made in captivity because of different
oMale ligers=infertile
oFemale liger=fertile
Hybrids are NOT considered a new species because they
are created in captivity and not in the wild
oMorphospecies Concept
Based on appearance
If they look alike they are alike
Ex, Peacock(male) and Peahen (female) look very different but are
still the same species
With this concept they would be considered different species
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Opposite is for butterflies, there ar 3 types that all look the same but
all have different configuration and # of their chromosomes, this
means that they could not sexually reproduce
oEcological Concept
Based on where they’re found in the wild and the role that they play
in their habitat
Consumer? Producer? Etc.
The role they play in their habitat Is called their niche
Now are able to define asexual organisms that reproduce asexually
Not easily tested for bacteria/microrganisms because they
can be found anywhere
oThere is no perfect way to define species but most commonly the
Biological Species Concept is used by scientists, then ecological
Biological Species concept is based on Sexual Repro.
Things that can get in the way of sexual repro.
o1. Genetic incompatibility
number/structure of chromosomes
if there are not homolgus chromosomes, synapsis does not happen
and they cannot repro.
o2. Temporal Isolation
repro. Cycles happen at different times
ex. Skunks that mate in winter vs. spring are incompatable
o3. Ecological Isolation
different environments
ex. Squirells on opposite sides of grand canyon can’t get across it
to mate
o4. Physical Isolation
Size, shape and position of sexual repro organs are different, may
be because of mutations
o5. Behavioral Isolation
courtship rituals differences ( albatross)
Formation of a New Species: SPECIATION
o“the process of forming a new species”
w/o speciation there would be little or no biodiversity
3.8 bil. Years ago 1 prokaryote made all the species
NEED TO KNOW! Genetic drift, natural selection and gene flow
Genetic drift
oRandom changes that happens in a neutral gene (gene that doesn’t
increase/decrease chances of survival)
oRandom changes happen because of CHANCE events
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Ex. Fish get ecologically isolated and then are able to form new
neutral change= change from blue to grey
doesn’t affect ability to survive
color changes because neutral gene mutates
oif 100% of pop. Takes on the mutated gene, the trait is “fixed” in the
Natural Selection
oEnvironment has a role/decides which genes will be passed on and which
ones are not
oBeneficial genes are the ones with increased likelihood of being passed
on and surviving in the pop. Because they will be passed on to their
oEx. Small fish mutates to large fish, the large fish #s go up because it is a
desirable trait because they have less predators and it is easier to find a
Pop of large fish goes up till it is 100% of pop and the gene/trait is
Gene Flow
oFlow implies migration
oThere are 2 populations
oPop. A are firtile, they repro. With pop B and “Mix Genes”
oThis decreases differences between populations
oDecreases speciation because the mixing of genes makes them so similar
oDoes not happen in isolated places such as islands because there are no
second similar population
Allopatric Speciation:
oFormation of new species in different places
oGeographically diff places with no gene flow
oEx. Galapagos islands no animals can get from mainland to islands
oEx. Galapagos finches
13 diff types of finches on the cluster of islands, all look similar and
most likely descended from 1 ancestor
some islands have seeds vs. flowers vs. fruit
the one with the ideally shaped beaks for the food type do much
better eventually 100% of the finches on an island all have the
same beak shape
the environment chose what the beneficial gene was
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