Task E-1 2-4
DNA - your genetic material.
A gene is a segment of DNA on a chromosome.
All the directions that control your growth is in DNA.
Your DNA is in a "double helix".
Task E-2 2-5
DNA is made of nucleotides.
There is a sugar/phosphate "backbone".
The nitrogen bases are:
adenine - A
cytosine - C
thymine - T
guanine - G
A - T Apple in the Tree
C - G Car in the Garage
Task E-3 2-6
When DNA replicates, it "unzips" in the middle.
Each half then has the "matching" nucleotide fill in to create two complete copies of DNA.
1. What "matches" adenine?
2. What "matches" cytosine?
Task E-4 2-7
replication - copying a DNA molecule, needed for cell division.
transcription - reading a section of DNA to create mRNA.
mRNA - a single strand of nucleotide that is used to make proteins.
Task E-5 2-10
RNA is like DNA, but uses uracil instead of thymine.
A = T in DNA
A = U in RNA
translation - making proteins with RNA.
tRNA - transfer RNA helps make proteins by putting together amino acids.
rRNA help ribosomes make proteins.
Proteins are made of amino acids.
1. What does the "t" in tRNA mean?
2. What does the "r" in rRNA mean?
Task E-6 2-11
RNA and DNA use three letter codes called codons.
The 64 different codons contain the instructions for assembling amino acids into proteins.
There are codes for starting and stopping transcription.
Task E-7 2-12
Charles Darwin - Wrote "Origins of Species" and he proposed evolution.
Evolution - life slowly changes over time.
variation - small differences among individuals in a population may be advantagous. It may allow for more food, or to escape predators.
Natural Selection - the individuals with the "most advantages" survive and reproduce. The offspring tend to have those advantages.
Darwin did NOT know about DNA or genetics.
1. Name several variations that could increase survival.
TASK E-8 2-13
Mutations - A change in the nucleotide sequence of a gene.
The nucleotides can be substituted,
a new one inserted, or an old one deleted.
Mutations can be passed on.
Mutations can also be caused by the environment
like radiation and chemical exposure.
Task E-9 2-18
Most mutations don't have any effect.
Some mutations make life impossible.
A few mutations are beneficial.
Beneficial mutations can help an individual survive and have kids.
The offspring may have the beneficial mutation.
Task E-10 2-19
Mutations help evolution.
Evolution is life changing over time.
Life began once on the Earth.
All life is related.
1. What animal do humans share 99% of genes with?
2. Who first proposed evolution?
Task E-11 2-21
The Earth is 4.5 billion years old.
Life was here about 4 billion years ago.
For 1.5 billion years life was all prokaryotes.
2.5 billion years ago Eukaryotes evolved.
570 million years ago was the Cambrian explosion, multicellular creatures start, trilobites were in the oceans, plants begin.
TASK E-12 2-24
We know the history of life on Earth by looking at fossils.
Life started simply, then slowly became more complex.
Precambrian era refers to only single celled, simple life.
We use names for "eras" because we knew about them
before we knew the dates.
A fossil is evidence of ancient life.
1. How long was single celled life on the Earth
before multicellular life?
Task E-13 2-25
There is evidence of five mass extinction events in the fossil record.
There are always some species going extinct and others dividing, but a mass extinction is when a large percent of species die at once.
They can be caused by a catastrophic global event, or widespread environmental changes that occur too fast for species to adapt.
Cambrian era refers to multi-cellular life forms starting on Earth.
This was 570 million years ago.
Ex. An asteroid hit the Earth, the dinosaurs became extinct.
Task E-14 2-26
The dinosaurs ruled the world for 150 million years.
Less time separates us from Tyrannosaurus rex than separated
T. rex from Stegosaurus.
Humans are only about 300,000 years old as a species.
During that time we have started the 6th extinction event.
TASK E-15 2-27
Darwin saw the birds and the tortoises were slightly
different on the islands of Galapogos.
The variations seemed to be adapted to each environment.
His theory of evolution fits all observations and is the
building block of all of biology and medicine.
1. What variations did birds have that showed adaptation,
how did it help?
Task E-16 3-2
All mammals share the same basic skeleton.
Giraffes have the same number of neck bones as we do.
Some bones can get bigger or smaller, but all are similar.
vestigial structures - body parts that aren't used anymore
ex: bones in whales for walking
Humans: appendix, wisdom teeth, coccyx (tailbone)
TASK E-17 3-3
The embryo is life as its developing before birth.
The embryos of many animals is very similar,
showing that we are related.
Molecular biology studies genes and functions.
We can now look at how species have changed over time.
Task E-18 3-4
Divergence - some DNA have mutations at a predictible rate.
We can use this rate of mutations as a "molecular clock" to see how related species are.
Mammals diverged from (dinosaurs) 250 MYA.
Red Panda - it was debated if the closest relative is a bear or a raccoon.
Using the "molecular clock" we know it is a weasel.
Task E-19 3-6
Adaptation - an inherited trait that increases an organism's chance of surviving and reproducing in its environment.
Adaptation drives natural selection.
There are three types of adaptations:
structural - bones or shells changing shape
behavioral - staying in herds or hunting at night
functional - changing the biochemistry
1. Name any adaptations that you know of...
Task E-20 3-10
Camouflage - adaptation that allow the organism to blend in with their environment.
mimicry - adaptation that causes the organism to resemble a different organism.
1. What type of adaptation is camouflage?
TASK E-21 3-11
Most of the history of life show slow changes, but after extinctions are "bursts" of change with lots of diverging species.
99% of all species that ever lived are extinct.
Current extinction rates are about 100 times "normal".
Read more: https://www.smithsonianmag.com/science-nature/on-dinosaur-time-65556840/#KJXWVlihAR8TV37X.99