EASY TO UNDERSTAND | Introduction to Evolution
Summary
TLDRIn this educational video, Miss Angler introduces the concept of evolution with a focus on phylogenetic trees, which illustrate the evolutionary relationships and divergence of species over time. She explains the significance of branches representing common ancestors and dramatic events leading to new species. The video covers four key pieces of evidence for evolution: fossil records, biogeography, descent with modification, and genetics. Each piece is detailed, emphasizing how they support the theory of evolution. The lesson concludes with a discussion on variation within species and populations, which is crucial for evolutionary processes.
Takeaways
- 🌳 Phylogenetic trees are essential for visualizing how organisms have evolved over time, with branches representing significant evolutionary events and common ancestors.
- 🕰 Phylogenetic trees provide a timeline of evolution, starting from the oldest organisms and progressing to newer, more complex ones, often measured in millions of years ago (mya).
- 🔍 The evidence for evolution includes fossil records, biogeography, descent with modification, and genetics, which collectively support the theory of evolution.
- 🦴 Fossil records indicate an increase in complexity and diversity of organisms over time, and the existence of transitional fossils that bridge evolutionary gaps.
- 🌍 Biogeography supports evolution by showing how the distribution of organisms across continents, which were once connected, indicates a shared evolutionary history.
- 🔬 Descent with modification illustrates how structures in different organisms have changed over time, pointing to a common ancestry and the adaptation to different environments.
- 🧬 Genetics provides strong evidence for evolution by showing the percentage of shared DNA among different species, indicating common ancestry and the degree of relatedness.
- 🧬🌐 Genetic similarities and differences among species are used to determine their evolutionary relatedness, with more shared DNA indicating closer relationships.
- 🧬🧪 Variation within species and populations, both continuous and discontinuous, is crucial for evolution, as it provides the raw material for natural selection to act upon.
- 📚 Understanding the concepts of species and populations, along with the types of variation, is fundamental for grasping the mechanisms that drive evolution.
Q & A
What is the main topic of the video?
-The main topic of the video is an introduction to evolution, specifically focusing on understanding phylogenetic trees and the evidence for evolution.
What is a phylogenetic tree and why is it important in studying evolution?
-A phylogenetic tree is a diagram that shows how organisms have evolved over time. It is important because it visually represents the relationships and common ancestry among different species, illustrating the timeline from the oldest to the more recent and complex organisms.
What are the four main pieces of evidence for evolution mentioned in the video?
-The four main pieces of evidence for evolution mentioned in the video are fossil records, biogeography, descent with modification, and genetics.
How does the fossil record provide evidence for evolution?
-The fossil record provides evidence for evolution by showing an increase in complexity and diversity of organisms over time, as well as the existence of transitional fossils that exhibit characteristics of both ancestral and descendant species.
What is a transitional fossil and why is it significant?
-A transitional fossil is a fossil that exhibits physical structures or phenotype similarities, making it an intermediate between different groups of organisms. It is significant because it provides evidence of the evolutionary process, showing how one species can evolve into another over time.
How does biogeography support the theory of evolution?
-Biogeography supports the theory of evolution by showing the distribution of species and their fossils across the globe. The presence of similar species in geographically separated areas suggests a common ancestry and supports the idea that species evolve in response to their environments.
What is meant by 'descent with modification' in the context of evolution?
-'Descent with modification' refers to the process by which organisms change over time as they inherit traits from their ancestors, leading to the development of new species. It is evidenced by homologous structures that have similar basic structures but different functions in different species.
How does genetics provide evidence for evolution?
-Genetics provides evidence for evolution by showing the similarities and differences in DNA among different species. The percentage of shared genes indicates the degree of relatedness and supports the idea of common ancestry among all living organisms.
What is the difference between a species and a population as defined in the video?
-A species is a group of individuals that can interbreed and produce fertile offspring, while a population is a group of individuals of the same species living in a particular habitat at the same time, also capable of interbreeding and producing fertile offspring.
What are the two types of variation mentioned in the video, and how do they relate to evolution?
-The two types of variation mentioned are continuous and discontinuous variation. Continuous variation refers to traits that have many possible values and intermediate forms, like eye color. Discontinuous variation refers to traits that have distinct categories with no in-betweens, like the color of the peppered moth. Both types of variation can lead to evolutionary changes as they provide the raw material for natural selection to act upon.
Outlines
🌿 Introduction to Evolution and Phylogenetic Trees
Miss Angler welcomes viewers to her biology class, focusing on an introduction to evolution. She announces a new series of videos that will replace her older ones on the topic. The video emphasizes the importance of understanding phylogenetic trees, which are used to visually represent the evolution of organisms over time. Each branch in the tree signifies a significant event leading to the emergence of a new group of organisms, all descending from a common ancestor. The video also mentions that these trees can represent a timeline, moving from older to newer and more complex organisms, often measured in millions of years ago (mya). The evidence for evolution is briefly introduced, including fossil records, biogeography, descent with modification, and genetics.
🐠 Evidence for Evolution: Fossil Records and Transitional Fossils
The paragraph delves into the first piece of evidence for evolution: the fossil record. It highlights how fossils demonstrate an increase in complexity and diversity of organisms over time. The concept of transitional fossils is introduced, exemplified by Archaeopteryx, which exhibits characteristics of both birds and reptiles. Transitional fossils are crucial as they represent intermediate stages in the evolutionary process, supporting the idea of common ancestry and divergence into new species. The paragraph also discusses how extinct and extant species contribute to our understanding of evolution through the study of their fossils.
🌐 Biogeography and Descent with Modification
Biogeography is presented as the second piece of evidence for evolution, explaining how the distribution of fossils across different geographical locations supports the theory of evolution. The example of Lystrosaurus found across continents that were once joined is used to illustrate this point. The paragraph then explores descent with modification, focusing on the pentadactyl limb as an example of how structures in different species can be homologous, indicating a shared ancestry. The discussion moves to the evolution of elephants, showing how species have modified over time from a common ancestor, with some becoming extinct and others evolving into modern species.
🧬 Genetics and Variation in Evolution
The final piece of evidence for evolution discussed is genetics. The paragraph explains how the sharing of genetic material between species indicates common ancestry and can be used to determine how closely related species are. The percentage of shared genes with other animals, such as chimps, chickens, and fruit flies, is mentioned to emphasize this point. The paragraph then transitions to the concept of variation, which is crucial for evolution to occur. It differentiates between continuous and discontinuous variation, using eye color and peppered moths as examples, respectively. The video concludes with a recap of the key terms and concepts covered, including species, population, and the types of variation.
Mindmap
Keywords
💡Phylogenetic Tree
💡Fossil Record
💡Biogeography
💡Descent with Modification
💡Genetics
💡Transitional Fossils
💡Common Ancestor
💡Variation
💡Species
💡Population
Highlights
Introduction to a new series of biology videos focusing on evolution.
Emphasis on the importance of understanding phylogenetic trees for studying evolution.
Explanation of how phylogenetic trees represent the evolution of organisms over time.
Description of branches in a phylogenetic tree as points of significant evolutionary change.
Mention of common ancestors as key points in the evolution depicted by phylogenetic trees.
Discussion on the timeline aspect of phylogenetic trees, showing progression from older to newer organisms.
Introduction of the four pieces of evidence for evolution: fossil records, biogeography, descent with modification, and genetics.
Explanation of how the fossil record shows increasing complexity and diversity in organisms over time.
Importance of transitional fossils as evidence for evolution.
Biogeography as evidence, showing the influence of land geography on the evolution of organisms.
The concept of modification with descent, highlighting the changes in structures as organisms evolve.
Genetics as evidence for evolution, showing the shared DNA among different species.
Discussion on how genetics supports the idea of common ancestors and relatedness among species.
Introduction of the concept of variation within species and populations as a driver for evolution.
Definition of 'species' in the context of evolution, focusing on the ability to produce viable offspring.
Definition of 'population' and its significance in the study of evolution.
Explanation of continuous and discontinuous variation in species and their role in evolution.
Terminology recap, summarizing key concepts discussed in the video.
Transcripts
hi everybody and welcome back to miss
angler's biology class i am miss angler
and in today's video we are going to do
an introduction to evolution this is a
new series of videos that are going to
replace my old videos and i'm going to
update these ones now with you now if
you're new here don't forget to give
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lessons with me and so much more
now as i mentioned earlier this
particular video is replacing my older
videos on evolution
it's just an updated version
so let's look at first of all this
diagram in front of us which is called a
phylogenetic tree you need to be very
comfortable in reading these when we go
through evolution because it's how we
express evolution
which is quite abstract and we we
express it in this physical
diagram way and essentially a
phylogenetic tree is showing us how
organisms have evolved over time and
each of these branches that we see here
on the diagram represent a point at
which something dramatic happened on
earth and it led to a group of organisms
arising in other words they descended
from somebody else and so every time
there's like a little notch in our
little tree over here it represents also
a common ancestor some particular
organism was very key in evolution that
we have left behind and that we have
created a
newer version of that organism or
that old common ancestor could still
even be around today
now the last basic thing we need to know
about phylogenetic trees is the fact
that they are showing us essentially a
timeline we're starting from the oldest
organisms and we're moving upwards to
the newer organisms and also the more
complex organisms generally not always
the case now in this diagram there isn't
a time scale but please know in exams
there will be and generally it is
counted in mya or millions of years ago
and they will ask you questions like
when did plants
arise or when did slime molds arise when
did they appear and so what you would do
is you would look at for example slime
molds over here you would look at where
do slime molds intercept with the
timeline and then you'd be able to tell
them how many millions of years ago but
that's the basics of how to use a
phytogenic tree
now we're going to briefly look at the
evidence for evolution and for your
tests and exams you need to know your
four pieces of evolution which is fossil
records biogeography descent with
modification and genetics sometimes this
is a question where they will literally
ask you name two types of evidence used
for evolution and these are the four
that you can give
now if they don't ask for an example
please don't give an example
and what i mean by that is if they say
name two types of evidence well you have
four to pick from here so only use these
four but if they said
name two types of genetic evidence for
evolution then you're going to say
something like mitochondrial dna or dna
and rna you're going to actually give
examples of each of these
now the first piece of evidence is the
fossil record and the fossil record
shows us three important things that we
will need to know for the exam
the fossil record shows us that
organisms over time become more complex
in other words their structures are more
complex
they become more diverse in other words
we started off with simply being a
simple
group of cells like protists and
bacteria and now we have arms and legs
and eyes and so many complex tissues so
we've become complex and we've become
diverse meaning we don't just have one
kind of
cell or one kind of bacteria we have
millions of different kinds of
microorganisms we have thousands of
different kinds of birds and reptiles
and mammals and so what the fossil
record shows us is that with time
organisms have become more complex and
they've become more diverse the third
and final thing that the fossil record
supports when it comes to evolution is
what we call transitional fossils
transitional fossils are fossils that
show organisms that seem to be an
intermediate or a mixture and examples
of these are things like the
archaeopteryx which is a mixture between
a bird and a reptile it has
characteristics that we see in both
groups and so we consider it a
transitional fossil and what these
transitional fossils show us is
organisms that sit somewhere in between
the two that allow us to then draw out
these family trees that we see alongside
you these phylogenetic trees that we
have here now some of these fish may no
longer be around for example all of the
fish here that have the cross next to
them are extinct however
they are all important key transitional
fossils that we have found that then
allow us to draw a full family picture
the remaining fish here the rayfin fish
lungfish and living tetrapods those are
the organisms we still see today and we
have their earlier onset ancestor
fossils available to us
now in the exam you are going to be
expected to explain what a transitional
fossil is so you need to be prepared to
explain that it is a fossil that
exhibits
physical structures or phenotype
similarities that make them an
intermediate in other words they have a
mixture of two different phyla or two
different groups of organisms
the next piece of evidence is
biogeography and as the name suggests it
references how geography of the land has
influenced the organisms that live on it
and what you're looking at here is when
all of these southern continents were
still attached to one another
and you see areas of fossils that are
shared amongst
these continents now this is only
possible if at one point all of the
continents were attached to one another
and this supports evolution because what
it says is
there's no way that an organism could
evolve to look and behave a certain way
if
it's found in multiple locations with
massive seas
and oceans in between the land masses
there'd be no way for this organism to
look the same
if it was divided into different
populations across giant oceans and as
an example to illustrate this if we
looked at the listosaurus it was found
across the african continent over
madagascar india and then antarctica
this is all where we find this fossil
now the fact that we can find the exact
same fossil for the exact same set of
years it only leads us to believe that
when the listosaurus first originated
and evolved and appeared in these
regions the land was joined together
which supports evolution because it
tells us that when the lystosaurus was
alive and it was adapting and evolving
it would have had to have done so over
the same land mass because if the land
mass separated and took the listosaurus
with it which it to some extent did when
india and africa and the antarctic
separated those organisms would start to
experience evolution independently
because their populations would be too
far away from each other for them to
interact or to interbreed with each
other
the next piece of evidence is
modification with descent and as the
name suggests
it refers to how structures and
organisms have modified over time and as
they've descended from their common
ancestor and we have a perfect example
of this when we look at the left hand
picture showing something called the
pentadactile limb it is essentially the
limb or the arm bone in most of these
organisms that is a similar structure
you'll notice that they've highlighted
the bones that are the same the humerus
the carpals metacarpals the phalanges
but you'll notice that they have changed
slightly they have modified and their
modification
represents a need to change in order to
be suited to their environment now
remember these organisms didn't want to
change they didn't force themselves to
change and we're going to go into more
detail about actually how does this come
about when we look at natural selection
but when we talk about modification with
descent we are talking about homologous
structures and these are structures like
limbs organs skeletal structures that
are similar in structure but they serve
different purposes and the fact that
they're so similar in structure can only
point to the fact that they evolved from
a common ancestor and therefore they're
all descendant
now this alternate picture i have on the
side here is a modification with the
scent but this time moving towards
modern elephants
and what it indicates is many different
uh groups of subspecies of evelephants
and also ancestors of elephants so here
is the current african elephant and the
current asian elephant at the very end
they are both alive currently but
everyone beyond that or should i say
below that no longer is alive they are
extinct
however what this diagram shows us is it
shows us an important aspect of common
descent which is a common ancestor now
common ancestors they are key in showing
genetic links
and more common ancestors means that
they are more closely related now what
does that mean for us in this diagram
well common ancestors represent these
individuals here these little points
and these common ancestors all the way
along wherever we see a little branch
off represent a key change something
that happened in the environment that
caused a branch off to happen and these
fossils of all these other predecessors
these primitive elephants if that's what
you want to call them they show us that
we have modified the elephant over time
some of the elephants have survived
until this point which is where we see
our current two elephants now but other
elephants have become extinct for a
variety of reasons it may be because of
their habitat has disappeared or perhaps
they've become extinct due to ice ages
like the mammoth but what we see here is
modification over time and you are
descending to where you are now in other
words what groups are still present on
earth
now the final piece of evidence is
genetics and when we speak about
genetics we are speaking about two major
aspects about what genetics can share
with us and the diagram i have a very
simple
outline here of all of the percentage uh
genes that we share with other animals
um we share 99.5 of our genes with
chimps 75
of our genes are shared with chickens
even 60 of your dna right now is exactly
the same as a fruit fly and so how does
genetics support evolution well the
first thing it does is it shows us that
genes and common ancestors must go hand
in hand we have to have a common
ancestor in order to share genes and so
all organisms have dna or rna in some
fashion which means we must be related
to each other there's no alternate and
the fact that all organisms genes cone
for the same protein in other words the
way in which a mouse makes muscle is the
same way a chicken makes muscle the same
way a human makes muscle we all make
these same structures in exactly the
same way and that means we have the same
genes
the second thing that genetics shows us
is how related we are and organisms are
based on their relatedness due to how
much chromosomal or how much
mitochondrial dna they share so the more
chromosomal or the mitochondrial dna we
share the more closely related we are
whereas the fewer chromosomal or mitral
chondrial dna we share the less we are
related the more distant we are
and so that's how we calculate
relatedness we see how much we have in
common and then how much we have that is
different and if we have more different
then we are obviously further related in
other words our common ancestor was much
much further back and that's basically
what we see here in this percentage of
genes it means that our ancestor with
fruit flies was much older than that of
the chicken the mouse and the chimp in
other words our common ancestor with a
mouse is much closer to us than the
common ancestor between humans and fruit
flies
now that we've looked at the evidence
for evolution the final key piece before
we look into well how does evolution
actually like happen we need to look at
one more thing and that is variation
there is variation at a species level in
other words you can see variation
between individuals but there's also
variation amongst a entire population
and so that means we need to look at all
the differences between the individuals
as well as the differences within
populations and these variations that we
see in our genes and our genetics helps
evolution take place
now these two words that i'm about to go
through now you must know off by heart
for your exams and you need to put some
key words in their definitions if they
ask for it the first one is species now
a species is a group of individuals that
are able to breed amongst themselves and
produce viable offspring viable means
that their offspring are fertile they
can make more of themselves an example
of that would be like two horses
reproduce and
they make a fertile offspring a fertile
baby horse however if you mix a horse
with a zebra
which you can do
they will not produce viable offspring
in other words the mixture between the
horse and the zebra the zos
will not be able to make more babies on
its own each time you would have to have
a horse and a zebra um combining
together the second word we need to know
is population now it's slightly
different to species you've got to see
the nuances and the difference
a population is a group of individuals
belonging to the same species
who
occupy a particular habitat it means
they live in a particular place at the
same time and are able to reproduce and
again produce viable offspring
the same time and same place is
important so the particular habitat and
the time is important because you can
have a population of elephants
in
kenya and then you can have a population
of elephants in south africa and you
have got to know which population you
were talking about they are the same
species they're just in two different
locations in two different perhaps time
sets but these two populations could
still meet one in kenya and one in south
africa and they could still reproduce
with each other
now when it comes to the variation that
we see in these species that we have
mentioned now there are two types
if we're talking about variation in a
species you can have continuous
variation or you can have discontinuous
variation and it's pretty
self-explanatory by these pictures but
essentially continuous variation means
there is a continuous or endless amount
of possible combinations and lots of
in-betweens and eye color is a perfect
example of that these are just some of
the eye colors that we see in humans but
anyone can be a mixture of these and
even newer colors that aren't on here
right now can appear especially if we're
mixing our eye colors together so it's
continuous on the other side we have the
peppered moth
and it shows discontinuous variation
because there's only two options it's
either a black moth or a white moth and
they're both the same species however
they just come in two colors it's
discontinuous because there's no
in-betweens
now as always i like to end off the
lesson with a terminology recap and you
can use these words for flash cards and
to study from for exams
we looked at the evidence that was used
for our evolution and we've got fossil
evidence which shows of course
complexity and diversity changing
we then looked at biogeography which was
the locations in which we find those
fossils and how those prove that they
evolved together at the same time
we have descent with modification which
is the change or the modification of a
organism's structure and that shows that
they originated as one structure and
it's changed over time in different
animals for for different reasons and
those particular structures are often
called homologous structures as i showed
you with that arm that we can see in
many different mammals but also birds
and amphibians
then we looked at genetics which showed
us how our similarities in our dna link
us together and how much we share
um it makes us more or less related we
spoke about common ancestors who are
organisms that are shared in our family
tree and they represent organisms that
have um
characteristics shared by our ancestors
that we don't necessarily see today
alive but they were alive at one point
and they exhibit physical
characteristics that are in us but also
in other
relatives we spoke about variation which
is the differences within ourselves and
in our genes and we looked at variation
in a species versus a population and we
looked at those definitions
i forgot to mention continuous and
discontinuous variation you remember
that continuous variation speaks about
like eye color and height with lots of
in-betweens whereas discontinuous speaks
about our
either ors either you have it or you
don't we saw that in the peppered moths
they're either black or they are white
and these kinds of variation leads to
opportunities for evolution to take
place
now if you like this video don't forget
to give it a thumbs up and subscribe and
i will see you all again soon bye
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