Activity

Activity

Evolution: a change in populations over successive generations.

Complete an Evidence Summary Chart as a class.

Identify one pro (positive) and one con (negative) argument for each area of evidence in the graphic organizer and one example for each of the two areas you were assigned.

Define the key terms related to each area of evidence.

Evidence for Evolution

Area: Embryology

Examples: embryo of pig and human

Pro: best evidence because it is the most fundamental or basic

information

Vocabulary: embryo — early stages of developing plants and animalscomparative embryology — study of

different developing organisms.

Comparative Embryology

Comparative Embryology

Evidence for Evolution

Area: Biochemistry

Examples: amino acid sequence of chimpanzee and human

Con: limited access to amino acids of past organisms

Vocabulary: comparative biochemistry — comparing amino acid sequences of

different organisms

If two organisms have similar DNA molecules, they have similar proteins. Similar proteins have similar amino acid sequences (orders). Thus, if amino acid sequences are similar, DNA of the organisms is similar.

Scientists believe that similar DNA sequences indicate a common origin. The more similar the DNA of two living organisms, the more closely related they may be to one another.

Hemoglobin, a protein in red blood cells, has been studied. Scientists know the specific amino acids and their arrangements in hemoglobin molecules of humans, gorillas, and horses.

Biochemical Evidence for Evolution


DNA Sequence -------> Amino Acid Sequence -------> Protein C A C G T T -------> valine histidine -------> Hemo.

Hemoglobin Amino Acid Sequence:Human: Val His Pro Gorilla: Val His GlyHorse: Val His Pro

This sample size is too small to provide accurate data. One must look at the entire amino acid sequence.

The more similar the sequences, the more closely related the organisms.


In this investigation, you will:

(a) count and record differences in the sequence of amino acids in similar portions of human, gorilla, and horse hemoglobin. (Table 1)

(1) (2) (3)

(b) count and record the molecules of each amino acid present in similar portions of human, gorilla, and horse hemoglobin. (Table 2)

(1) (2) (3)

(c) use these data to show how biochemical evidence can be used to support evolution.

Table 1. Number of Amino Acid Sequence Differences

Organisms Number of Differences

(1) Gorilla and Human

(2) Horse and Human

(3) Gorilla and Horse


Table 1 – differences in sequence

Table 2. Number of Each Amino AcidAmino Acid Abbreviation (1) Human (2) Gorilla (3) Horse

Alanine Ala

Arginine Arg

Aspartic Acid Asp

Cysteine Cys


* Each column should total 146

Table 2 - # of each type of amino acid


1. DNA codes for amino acids.

2. Amino acid chains form proteins.

3. Proteins perform specific functions.

4. Hemoglobin is a protein in red blood cells that carries oxygen.

5. Hemoglobin is found in all mammals.

6. It is similar in its amino acid sequence but not identical.

Amino Acid Sequence for Hemoglobin Molecule

Human (H) Chimp (C)

Chromosome comparison

Human (H)

Chimp (C) Orangutan (O)

Gorilla (G)

Chromosomes of Primates

What is a Mutation?

• A mutation is a permanent change in the DNA sequence (ATCG) of a gene.

Mutations in a gene's DNA sequence can alter the amino acid sequence of the protein encoded by the gene.

How does this happen? Like words in a sentence, the DNA sequence of each gene determines the amino acid sequence for the protein it encodes. • The DNA (ATCG) sequence is interpreted in groups of three nucleotide bases, called codons.• Each codon specifies a single amino acid in a protein.

Mutate a sentence!

We can think about the DNA sequence of a gene as a sentence made up entirely of three-letter words. In the sequence, each

three-letter word is a codon, specifying a single amino acid in a protein. Have a look at this sentence:

Thesunwashotbuttheoldmandidnotgethishat.

If you were to split this sentence into individual three-letter words, you would probably read it like this:

The sun was hot but the old man did not get his hat.

This sentence represents a gene.

This sentence represents a gene.

Each letter corresponds to a nucleotide base, and each word represents a codon. What if you shifted the three-letter

"reading frame?" You would end up with

T hes unw ash otb utt heo ldm and idn otg eth ish at.

Or

Th esu nwa sho tbu tth eol dma ndi dno tge thi sha t.

As you can see, only one of these three "reading frames“ translates into an understandable sentence. In the same

way, only one three-letter reading frame within a gene codes for the correct protein.

Mutation in Amino Acid Sequence for Hemoglobin Molecule

Evidence for Evolution Area: Genetics

Examples: domesticated plants and animals; DNA sequence; mutations

Pro: changes easily seen in domestic plants/animals; gene links for generation after generation documented.

Con: limited access to past DNA

Vocabulary: population — all organisms within a breeding group.

selective breeding — artificial selection of only the most desirable traits to be bred.

Domesticated Plants and Animals



cattle cats


corn

apples


Selective (artificial) Breeding

Certificate of Pedigree

Domesticated Plants and AnimalsSelective (artificial) Breeding



Human (H) Chimp (C)

Chromosome comparison

Human (H)

Chimp (C) Orangutan (O)

Gorilla (G)

Chromosomes of Primates

DNA Base Sequence Comparisons

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