Unit 8 Lesson 2: Biological Evolution Evidence

Question 1

You may have heard the phrase, “all life is connected.” Is this ture

Answer 1

This is true because all living things on Earth share a common ancestor that can be traced back to the earliest forms of life. Every species that has ever lived on Earth formed from existing species.

Question 2

Evidence of the common ancestry between living things are not always observed in physical traits.

Answer 2

For example, humans and banana plants look very different from each other. However, they do have similarities in their DNA (deoxyribonucleic acid), the molecule that carries genetic information.

Question 2

gene

Answer 2

a sequence of DNA that codes for a protein or nucleic acid, like RNA

Question 2

What is the strucure of an amino acid

Answer 2

Amino acids are made of the amino group (−NH2)
, carboxyl group (−COOH)
, and a side chain containing carbon, hydrogen, and/or oxygen. The amino group, carboxyl group, and side chain of the amino acid are all connected to a central carbon atom called the alpha carbon

Question 2

About 50 percent of the genes present in human DNA are comparable to a similar gene found in banana plants. What does this mean

Answer 2

These similarities in genes provide evidence of a common evolutionary ancestor between humans and banana plants.

Question 3

amino acids

Answer 3

a collection of 20 molecules that link together to form proteins

Question 3

The process by which organisms develop and change over time is called

Answer 3

evolution

Question 4

proteins

Answer 4

large molecules that are encoded by DNA and perform most functions for the cell

Question 5

What similar about the amino acids in all life on earth

Answer 5

Each of the 20 amino acids used by life on Earth have a unique side chain that makes them different from the rest, but they all have the amino group, carboxyl group, and alpha carbon.

Question 5

What happens when amino acids are joined together

Answer 5

When amino acids are joined together to make proteins, the carboxyl group of one amino acid is chemically joined to the amino group of the next amino acid, forming a chain of amino acids with a “backbone” made of the amino group, alpha carbon, and carboxyl group with the side chains dangling off the backbone.

Question 6

The unique sequence of side chains gives each protein its

Answer 6

unique shape and function.

Question 7

Different DNA sequences code for different orders of amino acids.What does this create

Answer 7

This creates proteins with different sequences of amino acids, creating different proteins with unique shapes and functions.

Question 8

Different DNA sequences code for

Answer 8

different orders of amino acids

Question 9

One piece of evidence for the existence of the last universal common ancestor is that

Answer 9

all life on Earth utilizes the same amino acids and the same code in DNA to make proteins.

Question 10

last universal common ancestor

Answer 10

a hypothesis presented by Charles Darwin that states that all life on Earth evolved from a single common ancestor billions of years ago

Question 11

Scientists analyze DNA and protein sequences to determine evolutionary relationships between living things. How

Answer 11

Since the DNA sequence determines a protein’s amino acid sequence, a gene shared by two closely related organisms often have very similar amino acid sequences. The closer the relationship between species, the more similar the amino acid sequence tends to be.

Question 12

Scientists use this sequence similarity data to build cladograms. What are cladograms

Answer 12

a specific type of phylogenetic tree in which all evolutionary relationships are linked back to a common ancestor shared by all species in the tree

Question 12

In the past, scientists had to use different tools to classify organisms. How did this change

Answer 12

Now that DNA analysis is available and all organisms share common DNA, genetic similarities and differences are useful to classify organisms.

Question 13

Why are amino acids called “the building blocks of life”?

Answer 13

Because they are the chemical “building blocks” of proteins which are the basis of all life on Earth.

Question 14

How can DNA analysis help scientists figure out how life evolved?

Answer 14

By looking at which amino acids exist in the DNA of living and extinct plants and animals, scientists can develop cladograms which show the relationships between those plants and animals over time.

Question 15

How do we know if two life forms are closely related to one another?

Answer 15

We analyze their DNA to see whether they are based on many of the same amino acids.

Question 15

Taxonomy

Answer 15

Taxonomy is one of the most important tools for understanding the process of evolution. Taxonomy is the classification of plants and animals based on specific qualities such as physical appearance and anatomy, internal organs, range, and behavior.

Question 16

Kisspeptin is an important protein for growth and development in many organisms. Scientists compared the amino acid sequences for kisspeptin in a rat, a human, and a chimpanzee. The human and the chimpanzee had more amino acids in common with each other than they had with the rat. However, all three organisms had an identical string of ten amino acids located in the same location in the protein.

Explain how the similarities and differences in the amino acid sequences related to the evolutionary relationships of these three organisms.

Answer 16

The similarities between chimpanzees and humans suggest that these two organisms are more closely related to each other than they are to rats. However, all three organisms share a close evolutionary relationship because they all have the same amino acid sequence in the kisspeptin protein. This suggests that they all have a similar DNA sequence that codes for this amino acid sequence. This similar sequence likely came from a common ancestor.

Question 17

In recent decades, evidence from DNA and protein sequences have also been used to classify organisms by

Answer 17

taxonomy

Question 18

How do scientists determine when species split from one another on the evolutionary tree?

Answer 18

One way to do this is using fossil evidence. You can use geological evidence to place fossils into certain time periods. You can then look for which time periods contain which fossils to determine when certain species came into existence and possibly split from one another.

Question 19

What are the ideas that lead to the molecular clock

Answer 19

In the 1960s, researchers Emile Zuckerandl and Linus Pauling hypothesized that DNA mutates at a constant rate. In addition, Motoo Kimura developed a theory known as neutral theory, which states that most mutations are neutral. By combining these two ideas, scientists use DNA mutations like a molecular clock.

Question 19

Scientists can determine when species split from one another on the evolutionary tree by using fossil evidence. What is the drawback of this

Answer 19

Unfortunately, the fossil record is very incomplete. Not all individuals become fossilized at death. So, how do scientists determine a common ancestor without finding the fossils to support it.

Question 20

What is the neutral theory

Answer 20

In addition, Motoo Kimura developed a theory known as neutral theory, which states that most mutations are neutral. In other words, most mutations neither provide an advantage or a disadvantage. These mutations either spread throughout the population or disappear by pure chance instead of being selected by natural selection.

Question 21

How does the molecular clock work

Answer 21

For example, if you compare the DNA of two different species and you find that their DNA differs by 6%, you can apply the idea of the molecular clock to calculate how long ago these species diverged from one another on the evolutionary tree based on the number of differences between them.

Question 22

What are the drawbacks to the molecular clock

Answer 22

First, it was later discovered that mutation rates differ from species to species and from time period to time period for various reasons.

Question 23

there are drawbacks to the molecular clock system as well. First, it was later discovered that mutation rates differ from species to species and from time period to time period for various reasons. Can the clock still be useful

Answer 23

Most scientists feel that the molecular clock can still be useful, especially over long periods of time, because you can use an average mutation rate. Even if the rate changes from time to time, the rate will be consistent on average, especially over long periods of time.

Question 24

What is another drawback to the molecular system

Answer 24

Finally, molecular clocks do require DNA analysis. Even under the best conditions, DNA is theorized to only last up to 1 million years. Therefore, fossils older than this do not contain any usable DNA. Because of this, scientists typically must use a combination of techniques to determine the dates for evolutionary branch points in phylogenetic trees.

Question 25

How might a researcher use DNA evidence to determine when winged animals first emerged on Earth?

Answer 25

They can use a combination of fossil evidence and the molecular clock, which is based on DNA mutation rates, to determine when winged animals first emerged on Earth.

Question 26

How might a researcher determine whether life forms from another planet are related to life forms from Earth?

Answer 26

They might compare the DNA of alien life forms to the DNA of Earth’s life forms to see if they are encoded for the same 20 amino acids.

Question 27

Which characteristics do all the animals have in common?

Answer 27

They are all vertebrates.