IB Biology A3.1 Diversity of Organisms
Summary
TLDRThis script delves into the diversity of life, discussing the distinctions between prokaryotes and eukaryotes, and the fundamental characteristics of living organisms. It explores the importance of genetic variation for survival and natural selection. The script also covers Carl Linnaeus's binomial nomenclature, the biological species concept, and the challenges in defining species, such as hybrids like mules and ligers. It touches on DNA's role in organism development, chromosome analysis, genetic diversity, and the implications of genome sequencing for understanding evolution, fighting diseases, and advancing personalized medicine. The script concludes with the creation of a dichotomous key and the innovative applications of DNA barcoding in species identification.
Takeaways
- 🌐 The Earth hosts a vast diversity of living organisms, with estimates ranging from 3 to 100 million different species.
- 🔬 Genetic variation within and among species is crucial for the survival of life, particularly through natural selection.
- 📚 In the 17th century, species began to be named systematically, and in the 18th century, Carl Linnaeus established the binomial nomenclature for consistent species naming.
- 🔑 The binomial nomenclature assigns each species a two-part scientific name: the first part is the genus, and the second is the species, both derived from Latin and written in italics.
- 🤔 The biological species concept defines a species as a group of organisms that can interbreed and produce fertile offspring, sharing a common gene pool.
- 🚫 Some organisms, like mules and ligers, do not fit the biological species concept because they are sterile and cannot reproduce fertile offspring.
- 🧬 DNA evidence has become instrumental in distinguishing populations and species, especially when traditional physical characteristics are not definitive.
- 🧬 Humans (Homo sapiens) have 46 chromosomes, which is close to chimpanzees, highlighting our genetic similarity despite differences in chromosome numbers.
- 🌱 Plants often have a higher tolerance for chromosome mutations, resulting in a wider variety of chromosome numbers compared to animals.
- 🧬 Genetic diversity arises from processes like crossing over during meiosis, which shuffles genes and contributes to the variation within a species.
- 🌐 Genome sequencing has revolutionized species comparison and classification, with the cost dropping dramatically from $100 million to about $1,000, enabling broader applications in science.
Q & A
What is the estimated range of different species living on Earth according to the National Wildlife Federation?
-The National Wildlife Federation estimates that there are three to 100 million different species living on Earth.
What is the importance of genetic variation within and among species?
-Genetic variation is essential to the survival of life, particularly through natural selection, as it allows species to adapt to changing environments and maintain their existence.
Who is credited with establishing the binomial nomenclature system for naming species?
-Carl Linnaeus is the primary scientist credited with establishing the binomial nomenclature system for naming species.
What are the two parts of a species' scientific name and how are they written?
-A species' scientific name consists of two parts: the genus (first word, capitalized) and the species (second word, lowercase). Both words are written in italics when typed or underlined when handwritten.
What is the defining feature of a species according to the biological species concept?
-The defining feature of a species is the ability to reproduce and have surviving and fertile offspring, sharing a common gene pool.
Why are mules and ligers not considered their own species despite being hybrid organisms?
-Mules and ligers are not considered their own species because they are sterile and unable to reproduce and have their own fertile offspring.
How does the process of natural selection contribute to the diversity of species?
-Natural selection contributes to the diversity of species by favoring certain genetic traits that enhance survival and reproduction in specific environments, leading to gradual changes and speciation over time.
What is the significance of the number of chromosomes in a species for its reproduction?
-The number of chromosomes in a species is significant for reproduction because it ensures that gametes (sperm and egg cells) have the correct number of chromosomes to form a viable zygote with paired chromosomes.
What is meant by the term 'genome' and how does it relate to species diversity?
-The term 'genome' refers to all the DNA, including all the genetic information of an individual. The genome sequence, including the number of base pairs and gene sequences, contributes to the diversity of species by encoding the characteristics that allow for adaptation and survival.
How does the process of crossing over during meiosis contribute to genetic diversity within a species?
-Crossing over during meiosis contributes to genetic diversity by exchanging segments of chromosomes between homologous chromosomes, creating new combinations of genes in the offspring.
What is DNA barcoding and how is it used to identify species?
-DNA barcoding is a technique used to identify species from small samples of DNA by comparing specific gene regions, such as the cytochrome C oxidase subunit I (Cox1) gene in animals, to a database of known sequences.
Outlines
🌿 Diversity of Life and Species Classification
The script begins by discussing the diversity of life, emphasizing the vast number of species on Earth as estimated by the National Wildlife Federation, which ranges from 3 to 100 million. It underscores the importance of biodiversity for the planet's ecosystems and the process of natural selection. The video then delves into the historical development of species naming, starting with Carl Linnaeus's binomial nomenclature in the 18th century. This system categorizes species into a hierarchical structure from domain to species, with each species having a two-part Latin name. The script also introduces the concept of the biological species, which are groups of organisms capable of interbreeding to produce fertile offspring. Exceptions to this concept, such as mules and ligers, which are sterile hybrids, are also mentioned.
🧬 DNA's Role in Species Identification and Hybrid Challenges
Paragraph 2 talks about the role of DNA in distinguishing species and the challenges posed by hybrids that don't fit the traditional biological species concept. It explains how populations, which are groups of the same species in the same area, can diverge genetically over time due to different environmental conditions, making species identification complex. The paragraph also discusses how DNA evidence aids in species identification and the significance of chromosomes in determining species. It mentions that most species have an even number of chromosomes due to sexual reproduction, with humans having 46 chromosomes. It also touches on the differences in chromosome numbers between humans and chimpanzees, highlighting the genetic similarity between the two species.
🧬 Unity and Diversity in the Genome
Paragraph 3 explores the unity and diversity within the genome, which is the complete set of genetic information for a species. It explains that members of a species share the same DNA and genes, although the sequences might vary slightly. The concept of crossing over during meiosis, which contributes to genetic diversity, is introduced. The paragraph also discusses genetic variation, specifically alleles and single nucleotide polymorphisms (SNPs), which are sources of diversity within a species. It mentions that while there is a significant amount of unity in the DNA among species, diversity is observed in the actual gene sequences and the number of base pairs.
🌐 Genome Variation and Species Diversity
Paragraph 4 discusses the variation in genome size and the concept of nonfunctional DNA, sometimes referred to as 'junk DNA,' which makes up about half of the human genome. It highlights the importance of comparing base sequences to understand the evolutionary relationships between species. The paragraph also addresses the challenges in defining species, especially when considering asexual reproduction and horizontal gene transfer in bacteria, which can complicate the application of the biological species concept. It emphasizes the importance of chromosome numbers being the same within a species for viable and fertile offspring.
🧬 Chromosome Consistency and Genetic Disorders
Paragraph 5 focuses on the importance of consistent chromosome numbers within a species for successful reproduction and the avoidance of genetic disorders. It explains that while the number of chromosomes can differ between species, they should be consistent within a species for fertility and viability. The paragraph also discusses the process of meiosis, which ensures that gametes have the same number of chromosomes, and how genetic disorders like Down syndrome can occur due to extra or missing chromosomes. Additionally, it touches on the concept of a dichotomous key for identifying species and the application of DNA barcoding for species identification from environmental DNA samples.
🔍 DNA Barcoding: A Tool for Species Identification
The final paragraph introduces DNA barcoding as a method for identifying species from small DNA samples found in various environments. It explains how this technique can be used in forensic science, food safety, ecological assessments, and the detection of invasive species. The paragraph highlights the wide range of applications for DNA barcoding and how it has become a valuable tool for scientists and biologists in species identification and environmental monitoring.
Mindmap
Keywords
💡Species Diversity
💡Genetic Variation
💡Carl Linnaeus
💡Binomial Nomenclature
💡Biological Species Concept
💡Hybrids
💡DNA Sequencing
💡Chromosomes
💡Genome
💡DNA Barcode
Highlights
The National Wildlife Federation estimates 3 to 100 million different species live on Earth.
New species are discovered and go extinct constantly.
Genetic variation within and among species is essential for survival.
Carl Linnaeus established the binomial nomenclature for naming species.
Species are categorized from domain to species in an upside-down triangle system.
Species have a scientific name with a capital genus and lowercase species name.
The biological species concept defines species as groups capable of interbreeding.
Hybrids like mules and ligers challenge the biological species concept.
Populations are groups of the same species in the same area at the same time.
DNA evidence helps distinguish populations and species.
Chromosomes are essential for species persistence, typically in even numbers.
Humans have 46 chromosomes, receiving 23 from each parent.
Chimpanzees, with 48 chromosomes, are genetically very similar to humans.
Plants have the most chromosomes due to their ability to tolerate mutations.
Karyotypes organize chromosomes by size, banding patterns, and centromere position.
Genomes consist of all an individual's DNA, with genes determining protein production.
Crossing over during meiosis leads to genetic diversity.
Alleles are alternate forms of a gene, often differing by a single nucleotide.
SNPs (single nucleotide polymorphisms) contribute to human diversity.
There is more genetic diversity between than within species.
Genome sequencing has become faster and cheaper, enabling species comparison.
Genome sequencing helps trace human migration, genetic diseases, and health.
DNA barcoding identifies species from small DNA samples.
The biological species concept faces challenges with asexual reproduction and horizontal gene transfer.
Transcripts
now that we've had time to discuss the
differences between procaryotes and ukar
as well as the overall characteristics
of living things in general we want to
turn our attention to what makes living
organisms different what is the
diversity of organisms and this is for
IB section a 3.1 on our planet there is
a wide diversity of living organisms the
National Wildlife Federation estimates
that there are three to 100 million
different species that live on the
planet which is really just astounding
regardless of where we're actually at in
that scale new species are being
discovered all the time and
unfortunately species are also going
extinct all of the time that variation
of life is essential to our existence on
the planet and to Life's existence on
the planet uh both within differences
between species and differences among
different species um and there's a wide
variety of of different types of species
on the planet as we see in some of these
pictures here genetic variation or
differen is within uh species and
amongst different species is really
essential to the survival of life and
particularly the survival of um life
through natural selection and so in this
video we're going to be examining how
are those differences um what are those
differences in in our variation of life
so today all species have a scientific
name and as humans we really like to
categorize things and so uh in the 17th
century this began to become a trend
where species that were discovered began
to be named and without some
organization uh there wasn't consistency
in in how different species were named
and so in the 18th century Carl anaus is
the uh primary scientist that began to
establish a naming system uh and he used
the morphology of an organism the
internal and the external structures to
help describe an organism as a species
and then species are groups that have or
had at the time similar traits today we
use uh and can use DNA sequen would seem
to be able to distinguish one species
from another but at the time it was
primarily based off of internal and
external structures uh and so Carl and
as developed what we now know as the
binomial nomenclature in which species
have two specific names and species are
divided um uh through a categorizing
system with the most broad being the
domain and then becoming more and more
specific as we see in our upside down
triangle where we start with the main
and then progress to Kingdom f class
order family genus and then species and
as we move down that list the
similarities between group um species
within those groups becomes more and
more specific and so how a species is
named it consists of two parts typically
it's of Latin Origins the first word in
a species name is always capital and it
designate the species genus the second
word in a species name is always
lowercase and this is the actual species
names and so for humans it would be Homo
sapiens where homo is the genus and
sapiens would then be the species uh
both of these words are always written
in italics if it's typed out or if it's
handwritten it would be underlined and
when we're using this in a text after
the first use um or or or writing of of
the species name it can be abbreviated
so that it's just the initial letter of
the genus and then the the species name
so H sapiens for homo sapiens and so
this is now how we name species so that
there is some consistency and it's used
worldwide by all scientists so
scientists in different parts of the
world can refer to the same species and
be clear about what they're actually
talking about so our next question then
is what defines or makes a species and a
biolog biological species is referred to
uh as the biological species concept
where this concept is the idea that a
species is an unchanging group of
organisms with differences both internal
and external from other species and and
as we'll get into a little bit later on
in the course species do change we we
know this through natural selection
because of changing environments um but
at any one point in time we can still
apply this as an unchanging group uh of
species in which the species the
organisms within that species are all
capable of breeding and have surviving
reproducing Offspring and that really is
the defining feature of what makes a
species is the ability to reproduce and
have surviving and fertile offspring so
that they can actually produce uh
species also share a gene pool and this
concept this idea works well for most
species but not for all uh sometimes
it's possible that species can intermix
and uh produce Offspring uh probably a
most common example of this would be a
mule uh which maybe you're familiar with
cross of a horse and a donkey produces a
a mule uh a living organism is it a
species it's kind of an interesting
question um scientists would generally
say no
it's not its own species because that
mule is sterile it's not able to
reproduce and uh a little bit more fun
example would be a liger which cross
between a lion and a tiger and
additionally the liger generally most
often are also sterile uh and so these
hybrids a mule or a liger while they do
exist as organisms it doesn't really fit
this uh biological species concept idea
in that an offspring is produced but
they're not fertile so they're not able
to reproduce and have their own
offspring that are fertile and so these
hybrids which also occur in Plants the
genus alium contains hundreds of species
onion and garlic in which the hybrids do
exist in natural habitats uh and so
sometimes most times this concept of of
what makes a biological species is
applicable to most species but not
always because of these hybrids uh we
don't see liers run around in the wild
because the lion and the tiger habitat
don't overlap mules we see in captivity
as well as ligers primarily in zoos and
so the idea of what makes a species fits
for most but not for everything and it
kind of goes back to this idea that
there's always kind of some exceptions
within biology uh Concepts or or rules
then based on this idea of a biological
species concept it is challenging to
distinguish populations and species from
one another uh what makes a population
is a group of organisms of the same
species in the same area at the same
same time and regardless of distance if
groups are genetically similar if we
look at their DNA and they're
genetically similar they are the same
species but separated species can
diverge over time and this is because
the environments that they're in may be
different and this can cause a group of
organisms a population within an area to
to change over time through natural
selection and they may develop
differences uh this would be a gradual
process and so it it makes it difficult
to determine whether populations are dis
distinct species or if they are the same
species and then what how much of a
difference must be present in order to
distinguish different species and so
this makes defining species difficult uh
and and it's a challenge and is easier
now that we're able to examine DNA
evidence to to help make some of those
decisions a good example of this we can
see with lions throughout Africa there
are different lion populations spread
throughout the continent they're the
same species Panther a Leo but they can
experience uh gradual changes due to the
specific environmental conditions of
where they're at and so those in Eastern
Africa might experience some um much
different environmental conditions
though than those that would be in South
Africa or western Africa and so that
makes it difficult to distinguish are
they different species or are they the
same species with slight variations in
their DNA and the general consensus
would be that they are all of the same
species currently on the on Africa we
have previously discussed how DNA is
essential for the development of
organisms and is responsible for all the
characteristics of an individual
organism and as for species for that
matter DNA typically is found within the
nucleus for eukaryotic cell organisms
and is contained within the nucleus and
is long wispy strand uh that's difficult
to organize as that cell begins to
prepare for duplicating uh for dividing
through mitosis the DNA condenses down
into chromosomes and we can look at
chromosomes and compare between
different species and when we do so we
see that each species typically um not
typically does have a different number
of chromosomes um and it's it's possible
that those number of chromosomes can
change uh throughout the ex existence of
the species though that would occur over
a very long per time periods and is not
very common most plant and animal
species have an even number of
chromosomes due to sexual reproduction
where half of the chromosomes are
received from each parent and so humans
for example we have a total of 46
chromosomes in which we receive 23 from
Mom and 23 from Dad combined to produce
46 uh these sex cells these gametes each
have half so sperm and egg each have
those 23 and those cells are referred to
or called haploid cells because they
have half the number of chromosomes a
body cell uh like a skin cell or a
muscle cell would then have a diploid or
two sets of chromosomes and that would
be the total of
46 our nearest closest relative in terms
of chromosomes and similarities in DNA
are the chimpanzees and chimpanzees have
48 chromosomes the differences between
these two species is only about 2% of
the DNA it's not very much at all and
the difference in chromosome numbers uh
is actually most likely from the
combining of chromosomes uh in humans so
we have two less than what chimpanzees
do having more chromosomes does not
necessarily indicate a greater
complexity of that species um but plants
actually are are the types of species
that have the most number of chromosomes
uh because they can tolerate mutations
that result in duplicate or extra
chromosomes uh humans and other
mamillion species are not able to
tolerate that as much typically the the
developing zygote the fetus would not go
on to develop because of too many or or
unmatching chromosomes so we're not able
to tolerate that plants can tolerate
that more often um and this is this is
most important in that all members of
the species have the same number of
chromosomes it's really important that
members of the species have the same
number of chromosomes in order for that
species to be able to persist so as we
just discussed chromosomes appear during
cell division uh specifically during
prophase of mitosis and we can view
these by staining the cells and viewing
under a microscope uh having those cells
uh burst so that the the chromosomes are
not overlapping allows us to actually be
able to take a look at them and how we
do that uh after we've taken the chromos
romes and organize them is uh called a
kot type and this is a kot type here
staining of the DNA this is not natural
colors but staining of the of the
different chromosomes uh allows for
banding uh banding patterns to to be
present for each chromosome they also
vary in size and then the position of
the central mirror which holds the two
arms together the chromatids together uh
this position varies and so this allows
us to line up the similar chromosomes
one from Mom one from Dad uh and we can
take a look at the chromosomes for a
particular species and make comparisons
within the species or of different
species and this kot type is uh of
humans because we can see there's 1
through 22 the autosomal chromosomes and
then we also have uh sex chromosomes X
and Y in this case to better understand
the similarities and differences between
genome sequences of different species
and within species we need to look at
the unity unity and diversity a genome
is all of the DNA the genetic
information of an individual and that's
what makes up the genome
members of a species have the same DNA
with the same genes uh not necessarily
the same type of forms and in the same
sequence so to be a member of the
species you're going to have the same
number of chromosomes those chromosomes
will have the same genes uh the sequence
might be slightly changed and we'll talk
about that in a moment during the
process of meosis uh which is the
production of sex cells sperm and egg an
exchange of portions of chromosomes can
actually swap places and this process is
called crossing over it takes place
during prophase 1 of meosis we'll learn
about it a little bit later on in the
course and it actually leads to genetic
diversity it's essentially just a way to
mix up the combination of uh types of
genes and this is possible because
members of the species have the same
number of chromosomes and genes and so
that's a Unity that's unity in that the
species have the same number of
chromosomes we see diversity then
expressed in the actual genes and So
within a gene sequence a gene is a
section of DNA that's responsible for
coding for some proteins has the
instructions to be able to make some
proteins we'll talk about that process
later on uh there can be different types
A very simple example uh the ability to
uh bend your thumb uh it's called a
hitchhiker's thumb uh you can bend it
back uh I can't really B Bend mine back
um but that ability is controlled by a
single Gene and what makes that ability
present or not present is by the
difference of a single Nu cleotide an a
TG or
C having that or not having that that's
a different form or a different type uh
and so what we call a different form or
an alternate form of a gene uh is an Al
um and another example this is very much
simplifying it but if we look at the
trait of eye colors uh that's the
particular trait that we're looking at
there are different obviously there's
different types or colors of eye colors
and so blue uh brown green uh Hazel
those would all be different types of
eye colors and those would all be
different alals for the the trait of eye
color eye color is actually a polygenic
trait which means it has multiple genes
that control it so it's actually much
more complex but that's just a simple
explanation uh to demonstrate what is an
Al differences are usually only a small
number of bases so what makes each Al
different from one another is just a
small number of bases so that difference
could be as simple as instead of having
a cytosine in one particular section of
the gene it might be a thyine uh or an
Adine and and the simple changing or
exchanging of just one uh nucleotide can
make a difference uh and result in a
different form of that Gene a different
Al positions in the gene where more than
one base may be present are called
single nucleotide polymorphisms or Snips
uh for shorts thousands of human genome
sequences indicate that there's about a
100 million different Snips uh but most
of the three billion uh are the same
there's Unity amongst our species U and
per human there's about four to 5,000
Snips or one base in every 650,000 and
this is a cause of diversity within the
species while this one base in every
650,000 may not seem like a great
difference uh that would lead to a lot
of variation this is actually one of the
main uh factors that contributes to
variation within the human species not
surprisingly there is a wide diversity
in the Genome of eukariotic species and
all living species on the planet there's
a far greater amount of diversity or
variation between different species than
there is within members of the same
species and the in terms of the
variation in genome size uh how big the
genome is or how much DNA there is is
based on the number of base pairs or
individual nucleotides and so large it's
actually possible for large genomes to
have lots of nonfunctional DNA meaning
that they don't result or um are used
for the production of proteins and
within humans this this is actually
about half of our genome uh they're
called transposons or transposable
sequences of DNA and they don't have a
known function we're not entirely sure
what what their purpose is uh in the
past or oftentimes are referred to as
junk DNA there is some evidence that
maybe what we thought was junk DNA is
not necessarily true in a nutshell we
don't exactly know how DNA is used for
all mechanisms of life and and
controlling life and we're still
learning much um a as time goes on and
Technology improves within the variation
sequence uh and comparing the base
sequence of different species over time
two populations can acquire more and
more genome bases and they can become
more distinct in in species as they
diverge from a common ancestor uh and
although changes are not common uh
partic changes are not always common uh
particularly in genes that have a vital
function um and this is because it
provides a selective Advantage uh or
disadvantage um and it results in not
changing uh and having um having the
gene stay the same between very
different species and we see this
sometimes uh in in vital genes such as
the cytochrome C uh it's a mitochondrial
protein and it's used during respiration
to maintain ATP production our cells
need ATP which is a cellular energy to
be able to to carry out their functions
and so living organisms have to have
that ATP and the gene that helps to make
that happen is very very similar uh
between lots of different species and
and very different species and that's
what's being displayed in the chart here
we can compare humans to other species
and we see that that Gene and the amino
acids that are used to make the proteins
from that Gene are really really similar
different species have different numbers
and and types of genes and genes can be
added or removed um uh as species
diverge from a common ancestor and so we
we typically see them to progress slowly
as they adapt to different ways of life
in terms of their genome diversity the
ability to compare organisms and to
classify organisms for that matter has
really improved drastically just within
the last decade uh and this is all based
off of sequencing the entire Genome of
an organism looking at the entire base
sequence of an organism uh this was
first completed in the 90s with bacteria
and rki now it's possible with pretty
much all organisms as long as the DNA
can be extracted and collected for
humans it was first completed in about
2003 with about 3 million base pairs
sequenced uh the speed and the cost is
what's amazingly uh how quickly it's
changed and improved in
2001 uh it was about $100 million to
sequence a human's genome today it's
about or in 2020 uh it's about $1,000
and so that is a massive difference in
cost and opens up whole new applications
to be able to compare species and really
learn and investigate about the
evolutionary origins uh of different
species we can identify relationships
between species we can trace common
ancestors uh we can learn how to fight
infectious diseases one of the reasons
that uh the vaccines for coid were
produced so quickly was the ability to
extract sequence and examine the DNA uh
between the different variants according
to science there's about 30 million
people that have had their genome
sequenced and for humans particularly
this provides information and data about
human migration genetic diseases human
health uh and it opens opens up all
kinds of new doors for potential
personalized medicine in the future and
this is already starting to to be more
and more common uh having genome
sequenced to be able to provide more
directed medical applications and
techniques the uh the process of genome
sequencing is just going to open up and
make available all kinds of uh new
technologies and capabilities that we
have not had in the past as we mentioned
at the beginning of the video the
concept of biological species works for
many species but not for all and so now
let's discuss some of the the challenges
with that uh within sexual reproduction
uh it it ensures that there's a mixture
of genes and uh ensures that there's a
unity in terms of the number of
chromosomes within a species uh and this
is regardless uh if the species can
reproduce both sexually and asexually
Sometimes some species have the ability
to do both in asexual reproducing
species however offsprings are clones of
parents that are produced uh via mitosis
and and a good example of this would be
like blackberries and dandelion if
you've ever seen a Blackberry before it
has this little arm that shoots out and
once that hits dirt it it starts a new
plant you could cut the the arm between
the two and then you have two distinct
plants but they're clones of one another
they're identical and so um it it's
essentially making copies like in a copy
machine if the Clones don't interbreed
with other clones then they're
technically a separate species by that
biological species concept and so
blackberries have hundreds of clones uh
dandelion quickly have have hundreds of
clones also and so it's difficult to
apply the idea of the concept of species
to these particular types of organisms
another example would be the horizontal
Gene transfer that can occur between
bacteria um this would be where parent
to offspring uh is typically a vertical
transfer the parent uh provides genetic
information to The Offspring uh
horizontal Gene transfer would be from
one organism to another not necessarily
parent to offspring and this is common
among bacteria there is so much Gene
transfer that can occur the species
concept may not even apply to
procaryotes uh and it's far less
frequent in UK carots and so how this
works is the the bacteria uh one in our
picture transfers a gene uh signified by
Red to the other bacteria number two and
this is transformation and so there
sending exchanging genes between one
another uh not from parent to offspring
but just between two different
individuals and so this also makes it
really difficult to distinguish are
these different species or are they one
species and so again not everything
exactly fits this concept of biological
species members of the same species
typically have the same number of
chromosomes uh and and that number is
oftentimes different than other species
in or for sex production male and female
produce gamut cells that have the same
number of chromosomes and these gametes
are formed by the process of meosis in
diploid cells so like a body cell
there's two sets of chromosomes one from
Mom one from Dad and each chromosome
carries the same sequence of genes uh
they may have different uh forms of
those genes alal and those chromosomes
that carry the same genes we call
homologous chromosomes because they have
the same genes although those genes
might be slightly different types during
meosis those homologous chromosomes pair
up to ensure an equal separation to each
gamt cell and this helps
to ensure that each gamt cell has for
humans chromosomes 1 through 23 uh in
each one of those different cells and
then when those gamt cells sperme egg
fuse the chromosomes then match up and
it produces a zygote uh if the cells or
the gametes have different number of
chromosomes
uh this usually results in some unpaired
chromosomes and often times this would
result in non-viable cells so the zygote
doesn't even develop uh at best
typically the The Offspring would be
infertile and unfortunately this is how
we see some of our genetic disorders uh
occur in humans for example Down
syndrome is uh an individual that has an
extra of chromosome 21 so they have
three chromosomes uh for 21 rather than
the typical two do and there are other
diseases that are also uh possible
because of of extra or deleted
chromosomes usually though the the cells
will not be viable and
So within species chromosome num should
be the same uh for the for The Offspring
to be fertile and to be viable uh
between different species the chromosome
numbers are going to differ so for this
learning objective students are expected
to produce a dichotomous key for a local
plant animal uh if you're one of my
students in class will actually do this
together uh if you're not and you're
learning from somewhere else would
recommend that you spend some time
researching how to make a dichotomus key
there are some general steps outlined
here and then actually go about creating
one for yourself and having some
practice and familiar familiarity using
a dichotomus key because you may be
expected to do so on the exam as I
discussed just a minute ago the ability
to sequence CNA has really opened up all
kinds of new doors uh and applications
for Science and here is one of those
applications what we we call DNA
barcoding and this is a tool used to
identify unknown species from small
samples of DNA DNA samples can be taken
from water soil basically any part of
the abiotic environment uh and the
locations will contain DNA from
individuals interacting with that
environment and so we leave DNA around
on a regular basis as do other species
those species can be compared by looking
at different Gene regions to be able to
identify uh the organism groups or that
particular species and most common for
animals and some protos is used the use
of cytochrome C oxidase or the Cox one
Gene and it's found in mitochondrial DNA
that Gene can be used to identify an
unknown species um there's large amounts
of possibilities uh for the use of this
this technique forensic science um
identifying individuals uh suspects uh
food safety ecological assessments uh
species identification invas invasive
species detection it has a wide range of
different uses and applications uh and
so it's a really cool tool that
scientists and biologists have now to be
able to uh compare sequences and
identify unknown organisms
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