EASY TO UNDERSTAND | Introduction to Evolution

Summary

In 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

00:00

🌿 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.

05:00

🐠 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.

10:04

🌐 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.

15:05

🧬 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.

Keywords

💡Phylogenetic Tree

A phylogenetic tree is a branching diagram that represents the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics. In the context of the video, the phylogenetic tree is used to express evolution by showing how organisms have evolved over time. Each branch point in the tree signifies a common ancestor, indicating a point in history where a significant evolutionary event occurred, leading to the emergence of a new group of organisms.

💡Fossil Record

The fossil record refers to the collective evidence of plant and animal life found within rock layers, which provide a chronological record of the history of life on Earth. In the video, the fossil record is highlighted as one of the key pieces of evidence for evolution, showing how organisms have become more complex and diverse over time. It also provides evidence for transitional fossils, which are fossils of organisms that appear to be intermediate forms between different species or groups.

💡Biogeography

Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. The video explains how biogeography supports evolution by showing the distribution of similar fossils across continents that were once connected. This suggests that species evolved in a common location and then dispersed as the continents drifted apart.

💡Descent with Modification

Descent with modification is a concept in evolutionary biology that refers to the process by which species evolve over time through the inheritance of genetic traits that are subject to mutation and natural selection. In the video, it is illustrated through examples such as the pentadactyl limb, showing how different species have similar limb structures that have been modified over time to suit their environments, indicating a common ancestry.

💡Genetics

Genetics is the study of genes, genetic variation, and heredity in organisms. The video uses genetics as evidence for evolution by discussing the shared DNA among different species, which implies common ancestry. The more genetic material two species share, the more closely related they are considered to be, supporting the idea of a shared evolutionary history.

💡Transitional Fossils

Transitional fossils are fossils of organisms that are intermediate in form or structure between established species, providing evidence of the evolutionary transition from one species to another. In the video, examples like Archaeopteryx are used to illustrate how these fossils show a mixture of characteristics from different groups, supporting the idea of evolution.

💡Common Ancestor

A common ancestor is a species from which multiple other species have evolved. The video explains that every branch point in a phylogenetic tree represents a common ancestor, indicating a key organism in the evolutionary history that has given rise to new lineages or is still present in the form of its descendants.

💡Variation

Variation in biology refers to the differences in traits or characteristics among individuals of the same species. The video discusses how variation at the species level and within populations is crucial for evolution, as it provides the raw material for natural selection to act upon. Variation can be continuous, like eye color in humans, or discontinuous, like the color of peppered moths.

💡Species

A species is a group of living organisms that can interbreed to produce fertile offspring. In the video, the concept of a species is used to explain how a group of individuals that are able to breed amongst themselves and produce viable offspring are considered the same species, which is a fundamental unit of biodiversity and evolution.

💡Population

A population is a group of individuals of the same species that live in the same area at the same time and have the potential for interbreeding. The video distinguishes between species and populations, highlighting that populations can exist in different habitats and times, and are important units for studying genetic variation and evolution within a species.

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

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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