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Last Minute Biology EOC Cram Session // 25min Crash Bio Review!

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hello everyone and welcome to this

year's last minute crash review for your

end of course biology exam this video is

for students who are about to take a

final course test EOC or state exam in

biology that means you might be in 9th

or 10th grade right now but that may

vary depending on your school or state

in this video I'm going to quickly

review some really important content

that's commonly questioned on the end of

course biology exams and review some

basic skills that might pop up on your

test remember this is a fast review so

it won't cover everything you learned in

biology and I do talk fast so feel free

to change the speed on your video player

if you need if you need to go back and

do a deeper dive on any of these topics

make sure to check out the other

resources on my channel let's get

started very briefly remember all matter

on earth is made of different elements

elements are composed of different atoms

and in biology we really want to focus

on molecules called organic compounds

now these are special molecules that all

contain carbon that are essential for

life and the forming categories are

nucleic acids proteins carbohydrates and

lipids so we look at what they're made

of the monomers or the basic units of

nucleic acids are nucleotides the basic

monomers of proteins are amino acids and

carbohydrates the monomers are

monosaccharide and the basic monomers of

lipids are often fatty acids and

glycerol now up here I have the basic

structure as well this is actually a

phospholipid which makes up the cell

membrane of all living things and we'll

get to that in a little bit now to

remember all of these organic compound

groups I like the pneumonic clean later

party now for carbohydrates lipids

proteins and nucleic acid acids one

thing I like to add to this is clean

later party especially now to remember

that enzymes for that e are a type of

protein which is really important

enzymes are really important biological

macro molecules and they belong in the

protein category now let's talk about

water really quick water is the

universal solvent it is polar that means

it's partially positive and partially

negative on opposite ends so some

molecules are water loving we call these

hydrophilic and they interact easily

they're soluble with water

hydrophobic or water fearing molecules

like oils and fats are insoluble in

water now water has special properties

it has cohesion meaning water is

attracted to itself adhesion is the

attraction of water molecules to other

molecules or other things thinking

adding something on capillary action is

when cohesion and adhesion work together

pulling up against gravity we can see

this in stems in plants or in a straw

even and water also has a high surface

tension meaning it's more attracted to

itself then the air around it which

allows certain bugs like Strider bugs

and leaves to float on the surface of

water now let's get microscopic and go

down to the cell remember cells are the

basic units of life so all living things

have cells all cells are surrounded by a

cell membrane which is a phospholipid

bilayer we talked about lipids all

living things contain genetic

information DNA and all cells have

cytoplasm now if we look just at the

cell membrane let's zoom in really

closely it is actually a layer of two

rows of phos phospholipids so are Bayer

uh the heads of these fosol lipids are

hydrophilic so they are able to interact

with water easily the inner parts the

Tails here they're ranging themselves

away from the water because they are

hydrophobic now there's two main types

of cells we have eukaryotic cells which

have a nucleus and membranebound organel

like the mitochondria and then we have

procaryotic cells which also are

surrounded by membrane and also have DNA

but they do not have a nucleus and they

do not have membrane bound organel they

do have ribosomes they do have a

cytoplasm but we notice here the DNA

which is the scribbles on the diagram is

just floating freely in the cytoplasm

unlike the DNA and eukaryotic organisms

which is in the nucleus now eukaryotic

organisms can be animals they can be

plants and procaryotic organisms are

mostly bacteria we have archa as well

within our eukariotic cells we have

different types for example animal cells

over here which have a cell membrane and

plant cells which are also surrounded by

a cell wall for extra protection and

support another key difference between

plant and animal cells is the presence

of a chloroplast which is shown right

here chloroplasts are the location of

photosynthesis which plants perform

animal cells do not plant cells also

have one rather large vacu and animal

cells also have a vacu but um it's not

as big and they may have several

different vacul as well and remember

both plant and animal cells plant and

animal cells are both eukaryotic now

let's zoom in once again on that cell

membrane remember it is made made of a

phospholipid Bayer now different

molecules can get in and out of the cell

membrane in different ways we have

simple diffusion which is the movement

of particles from a higher concentration

to a lower concentration we have

facilitated diffusion which allows

particles to move from a higher

concentration to a lower concentration

but across a membrane facilitated being

helped this protein channel is helping

the molecules get through the membrane

then we have active transport which

allows molecules to move from a low

concentration to a higher con

concentration with the help of energy in

the form of ATP so a way I like to

remember this is kids going down the

slide so simple diffusion requires no

energy it's just a kid going down the

slide from high to low by themselves

facilitated diffusion might have a

parent or a friend which is

representative of our protein and

they're going from high to low as well

still requiring no energy themselves and

then active transport think of a child

going from low to high going up the

slide so against the concentration

gradient but they have to use energy to

do that so they're using ATP all right

when water moves across a membrane this

is called osmosis this is water moving

from a higher concentration of water

particles to a lower concentration of

water and when we think about where the

water is moving and comparison to the

solute or the other particles dissolved

in the water solution here we have kind

of an equal balance of particles in and

out of the cell that are not water so we

would call this an isotonic solution and

water would move freely in both

directions and about the same amounts in

this situation we have a higher

concentration of particles or solute

inside the cell but a higher

concentration of water particles which

is the blue here outside of the cell so

where would the water move the water

would move into the cell this is a

situation called a hypotonic solution

where there are fewer solute particles

outside the cell more inside the cell

more water outside the cell a lower

concentration of water inside the cell

so water would move in and now here we

have more solute particles out outside

the cell or a higher concentration of

solute particles so remember where is

water going to move from a high

concentration of water so that means it

would move outside the cell this is

called a hypertonic environment now in a

hypertonic environment there is a chance

that if a lot of water moves out of the

cell the cell could actually shrink and

the opposite would happen in a hypotonic

environment a lot of water may move into

the cell causing it to swell or burst

let's get back to enzymes remember these

are a type of proteins they are

extremely important to living things

they are biological catalysts meaning

they get things going they get reactions

started things like ligase helicase

polymerase amase these are all enzymes

notice all of these words and in the

letters as e which makes it easy to

recognize an enzyme even if you've never

seen it before some things that can

affect enzymes are temperature or pH if

enzymes get too hot they can denature or

unfold and then they'd be unable to act

with their substrate because they no

longer have the shape of the active site

which is where a protein or an enzyme

usually interacts with the substrate the

molecule that it's going to do something

to or interact with all right let's jump

over to cellular respiration now all

living things need energy and one of the

main ways they get that is through

cellular respiration which occurs in the

mitochondria this is the process where

organisms take glucose sugar and oxygen

and go through reactions to transform it

into ATP energy in that process carbon

dioxide and water are also generated so

if we think about this on a larger scale

when we eat we consume glucose when we

inhale we take in oxygen and when we

exhale that CO2 is a byproduct of

cellular respiration we exhale water

vapor as well you can see that coming

out of your mouth on a cold day and then

ATP is also generated which gives us the

energy to perform our daily activities

and survive all eukaryotic organisms are

going to perform some type of

respiration another important reaction

we need to be aware of is photosynthesis

this is how plants get the food they

need and they use sunlight energy to

convert the carbon and carbon dioxide

into food molecules like glucose so

carbon dioxide in the sunlight energy

and water can be transformed into

glucose and oxygen remember the plants

need that glucose and oxygen to perform

cellular respiration themselves so these

processes are complimentary and they

feed each other which is why

photosynthesis is crucial to life on

Earth another type of respiration is

fermentation this is often called

anerobic respiration it's a type of

anerobic respiration but that means it

occurs without oxygen so bacteria some

yeast perform this process and

fermentation is not as efficient as

cellular respiration cellular

respiration produces 36 molecules of ATP

where fermentation only produces two

molecules of ATP so even though we can

also perform fermentation in our muscle

cells for example when we run out of

oxygen cellular respiration is a much

more efficient efficient process for

producing energy molecules so like I

said the type of fermentation that we

can do in our muscle cells is called

lactic acid ferment ation and that's

because we take glucose and we generate

energy molecules ATP but also lactic

acid as a byproduct now yeast can do

another type of fermentation called

alcoholic fermentation and here the

yeast produce ethanol as a byproduct or

a type of alcohol and carbon dioxide so

that carbon dioxide we can see as

bubbles forming if you've ever done an

experiment with yeast and fermentation

it's why Bakers use yeast in their

baking because that carbon dioxide can

help bread rise and then also of course

ATP is generated in this process let's

get down to the DNA in our cells

remember all living things contain DNA

now DNA is organized it is wound up into

chromosomes and condenses into

chromosomal form before the cell can

divide remember each double-sided

chromosome that looks like this actually

is a duplicated set of DNA so we have

two sister chromatids here they're

connected at the center by a centrr but

usually within the cell if the cell is

not preparing for cell division it may

not be condensed into these chromosome

forms it may may just be in chromatin

form which sounds similar to chromosome

but it kind of is represented as this

like spaghetti like drawing where the

DNA is Unwound it's not condensed as the

cell prepares for cell division we may

see the chromosomes begin to look like

this that means the DNA has already been

duplicated and the chromosomes are

arranging themselves so they can prepare

for cell division mitosis is a type of

asexual reproduction where cells make

exact copies of themselves one cell can

generate two identical daughter cells

you might have learned the phases of

mitosis as Pat which stands for prophase

metaphase anaphase and telophase and

then at the end there's cyto Kinesis

where the cytoplasm actually divides now

in prophase the nuclear envelope

dissolves and the chromosomes condense

they start to move to the middle of the

cell and metaphase they align along that

cellular equator or the center of the

cell and these spindle fibers on

opposite ends of the cell come and

attach the cir in anaphase think a for

away the cytochrom are separated they

start to get pulled away from each other

towards opposite ends of the cell in

telophase new nuclear envelopes start to

form the cell starts to separate and

inside a Kinesis we have the exact

separation of the cytoplasm now with

mitosis you've probably also studied

meiosis which is a different type of

cell division mitosis remember will copy

body cells make exact duplicates of

cells so one parent cell will create two

identical daughter cells whereas meiosis

is the process used to generate sex

cells so one parent cell that goes

through meiosis will generate four

daughter cells but they'll only have

half the genetic information as the

parent cell so meiosis takes a little

bit longer it goes through pmac twice

and you don't need to memorize what

happens in every single stage but the

results are important so at the end of

meiosis there are going to be four

daughter cells each with half the

genetic information as the parent cell

and this genetic information has been

mixed up a little bit so it's a

different combination in each cell so

the genetic information is different at

the end of meiosis which is going to be

helpful in the diversity of life on

Earth as organisms reproduce sexually

now as organisms reproduce we pass on

our genetic traits Gregor Mandel was

often called the father of genetics he

did studies that recognize that a lot of

traits are controlled by two different

alals or versions of a gene and alals

can be dominant or recessive meaning one

can cover up a particular trait so we

have these words heterozygous homozygous

to talk about genotypes or combinations

of genes so for example this big T Big T

would be a homozygous dominant genotype

and each of these letters represents a

version of that Gene so you could pause

and try to fill this in for yourself but

here we go we have big T Big T would be

homozygous dominant Big B little B would

be heterozygous because it's two

different versions of the same gene and

Little T Little T is homozygous

recessive two different versions of the

recessive gene remember a big T often

represents a dominant Al and a little or

a lowercase letter would represent a

recessive Al so for example if yellow

body color is dominant to Blue in these

fish if we have a Big Y and a little y

that would result in a fish being yellow

that's the phenotype so if we write the

phenotypes here we would see what would

happen with each of these genotypes

remember genotypes are the combination

of genes phenotypes are the actual

physical character istics that we get

from the genotype so you can pause this

and go through each of the examples if

you want and you might have also

practiced punet squares in biology where

you have to separate the alals of both

parents on this table and figure out the

possible combinations that could result

from this Cross or from when these

parents mate what their offspring could

potentially have and remember what

happens in a punet square is just a

probability it is a potential outcome we

won't know for sure until the off spring

are born what the actual genotypes and

phenotypes are and remember most human

traits most genetics are very

complicated so it's not as simple as

Gregor mandelle said there's different

types of dominance like incomplete

dominance where there's a blending of

traits co-dominance where we see

representations of both traits so for

example if a purple and a pink flower

were co-dominant for flower color we

might see both purple and pink petals in

their flowers and of course there's also

sex linked traits which are traits that

are carried on the ex and the Y

chromosomes now humans have 23 pairs of

chromosomes that 23rd pair is going to

be the sex chromosomes and females have

two X chromosomes males have an X and A

Y we talk about traits like color

blindness these are traits that are

carried on the chromosomes that are sex

chromosomes so when we perform genetic

crosses with sex linked traits we'll

also write the X and the Y there and the

alil as an exponent and make sure we

carry all of the letters together in our

punet Square cross process now genes can

also be influenced by the environment

for example these hydrangeas can have

different colors based on the pH of the

soil and this can go for a lot of

different traits sometimes there's

temperature differences that can change

the color of fur of different mammals

and of course chromosomes can have

problems separating during meiosis or

mitosis and when we have that

non-disjunction or those sister

chromatids not going to the opposite end

of the cell correctly we could end up

with a cell with different numbers of

chromosomes for example triom 21 would

mean that we have three copies of the

21st chromosome and triom 21 is also

known as Down syndrome and that mean

that person would have a condition that

affects their physical characteristics

some of their development because of

that extra copy of that chromosome now

let's talk about DNA a little bit closer

now remember that in DNA we have four

different bases A's T's G's and C's a is

always pair with t g is always pair with

C DNA replicates during the S phase of

the cell cycle and in DNA replication we

have the DNA strand separating and new

strands of DNA are built off the templat

so it's called semiconservative

replication each new strand of DNA has

half the old Strand and half brand new

if we look back at our organic compound

structure each nucleotide has a

phosphate a sugar and a base atg or C

and so when we put these together A's

and T's we can see always pair together

with these are little hydrogen bonds in

the middle G's and C's always pair

together and the backbone of the DNA

molecule is made of phosphate and sugar

molecules so how do we get exactly from

our DNA to our actual trait well the

process is called protein synthesis and

in the nucleus where the DNA is the DNA

will separate and then an mRNA sequence

will be built off of the DNA template

that mRNA will leave the nucleus and

that process is transcription then we'll

go through translation where the MRNA

will go to a ribosome and tRNA molecules

a different type of RNA will match up

with the codons or the different groups

of mRNA and bring over a matching amino

acid and then those amino acids will

start to link up and remember amino

acids make proteins and so that is how

we deliver the message to build the

protein that is going to give us some

trait in our bodies like the protein

that influences eye color or the protein

that gives us our hair shape so some

differences to remember between DNA and

RNA DNA is double stranded RNA is single

stranded DNA has actually a deoxy ribo

sugar that's where its name comes from

deoxy ribonucleic Acid where RNA is made

of a ribo sugar and then DNA's bases are

A's T's G's and C's where RNA actually

has a u instead of a t so if you're

creating an RNA strand based off DNA

remember to replace wherever a t would

go with a u let's do a little practice

so if we're transcribing a sequence of

DNA this purple is the DNA here the

sequence is a g t g t c the

complimentary RNA would be a pairs with

u g pairs with C T pairs with a G pairs

with C T pairs with A and C pairs with G

so again try this on your own go ahead

and pause real quick the correct mRNA

sequence here would be a ug CG auu and

then don't forget the next step is

translation where we build that protein

and to do this by hand you might see a

codon chart where you're asked to find

the codon and then the matching amino

acids so let's say we were looking at a

codon that was CCC so we'd start in the

center find the C then find the next C

in the next Circle and then go to the

final Circle here find that c that

refers to Pro which is short for Proline

one of our amino acids you do not need

to memorize all your amino acids and if

you're ever asked to do translation on a

biology exam you will be provided with a

codeon chart codeon charts can also look

like this so let's look at CCC again C

is our first base here we would go to

the top for our second base here's

another C and then find that third base

C that also corresponds to Proline on

this chart it is a universal genetic

code let's talk really quickly about

biotechnology now there's lots of

different growing and emerging new

technologies in the field of

biotechnology from lab grown meat to DNA

tests to genetically engineered

organisms to resurrecting woly man

Mammoth to crisper DNA and so of course

there's ethical questions that go along

with all these new techniques one

technique you might see on your exam

would be gel electropheresis which is a

way to identify different parts of DNA

so gel electropheresis can be used to

study evolutionary relationships

identify DNA found at crime scenes or

maternity or paternity testing so here

we have a simple gel in the gel DNA is

loaded at these Wells at the top DNA is

negatively charged so it'll be attracted

towards the positive and then these DNA

samples will travel down this gel as we

run an electric current through the gel

and we can see which pairs match up so

here we have a mother which matches with

child a and child B child C though does

not have any matches with the mother so

we can say that child C is not related

to this particular mother and on a much

larger scale remember that evolution is

the change in genetic makeup of a

population over time natural selection

is the major mechanism behind Evolution

and when we talk about an organism Being

evolutionarily Fit that means means how

well they are able to survive and

reproduce not how strong they are not

how fast they are it's really about how

they can survive and pass on their

traits to their offspring and remember

that environments are a huge factor in

evolution and they can act as a

selective pressure and different

organisms will have better rates of

survival in different types of

environments an adaptation is an

inherited trait that is favorable to an

organism that helps an organism survive

and Charles Darwin was one of our main

scientists that created this idea of

natural selection we have lots of

evidence now to support this idea of

evolution from the fossil record to

biochemical and DNA evidence embryology

we can see how different organisms

develop very similarly through the study

of their embryos a philogenetic tree or

a cladogram is a way to look at

different evolutionary relationships

over time and when we see branches on a

tree we can see where their last common

ancestor might have been and we can also

add traits to this tree so if we look at

a tree like this we can read it as

anytime there's a trait that appears any

organism that comes after that trait

developed that trait so for example the

organisms on this tree that have

vascular tissue are ferns pine trees and

flowering plants but not mosses and the

organisms or the groups of organisms

that have seeds are pine trees and

flowering plants but not Ferns and

mosses now backing all the way up to the

biosphere remember different levels of

organization in biology go from molecule

all the way up to all life on Earth and

at the population community and

ecosystem level we can talk about

biodiversity which is a measure of the

variety of different types of organisms

in an ecosystem and biodiversity is very

important to living things because the

more biodiverse an ecosystem is the more

resilient it will be now of course

environments are always changing large

scale changes that can influence

ecosystem can be maybe the addition of

different nutrients to a system we could

have forest fires we could have droughts

we could have floods earthquakes there's

so many things that could influence and

create major changes to an ecosystem in

a food chain we can see that organisms

that produce their food often come first

so producers like these autot tropes or

grass are here and we always drew the

arrow pointing towards the organism that

is doing the eating so think about this

food going into this Elk's stomach

that's the direction of arrows for a

food chain or a food web now we have our

producers or our autotrophs here are

heterotrophs are organisms that get

their food from something else so they

don't make it on their own they consume

their food this is also a heter trro and

this is also a hetro and when we go up a

food chain or a food web we can also

identify organisms as producers or

consumers so this is a producer this is

a primary consumer because it's the

first organism that eats the producer

this is a secondary consumer and this is

a tertiary consumer if the human were to

eat the Bobcat on a trophic pyramid

remember that the most energy is found

at the bottom of the pyramid and as you

go up a level most of that energy is

lost to the environment so it's more

efficient to consume lower on at trophic

pyramid if you're an organism there are

tons of different mod molecules and

atoms cycling throughout our environment

carbon is one of them and the carbon

cycle involves both photosynthesis the

plants harnessing sunlight energy in

order to take the carbon dioxide from

the air and create glucose molecules

respiration we take that glucose and we

use it to create energy and then we

exhale the carbon dioxide decomposition

can break down carbon in organisms

bodies and combustion also releases

carbon dioxide into the environment now

there are tons of resources on Earth

some are renewable which means they can

be replaced quickly by natural processes

some are non-renewable meaning they

cannot be replaced generally within

human lifetimes or as fast as they are

being used and so we need to consider

the our use of resources as the

population of humans continues to boom

on planet Earth a hole in the ozone

layer is a problem that we've identified

recently but it's actually getting

better but this hole produced by the use

of cfc's or a chemical called

chlorofluorocarbons was pretty dangerous

cuz it was letting in armful UV

radiation into the earth now this is

separate from the issue of global

warming which is predominantly affected

by the combustion or burning of fossil

fuels because that adds gases to the

atmosphere that cause it to hold more

heat and continued global warming can

lead to rising sea levels coastal

flooding but there are other human

impacts plenty of human impacts on the

environment such as introduction of

invasive species introduction of

diseases changing habitats

deforestation industrialization all of

these things but humans can also have a

positive impact on the environment by

reducing our consumption of resources

recycling planting native species

protecting wildlife and habitats and

supporting sustainable practices wo

we're coming to the end I hope this has

been helpful as you cram for your

biology exam I have lots of other

biology AP biology and other life

science resources on this channel so be

sure to subscribe so you don't miss out

best of luck on your biology exam let me

know if you have any more questions in

the comments below thanks so much for

watching and give this video a like if

it's been help helpful I'll see you later

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