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
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.
Biochemical Evidence for Evolution
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
Biochemical Evidence for Evolution
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
Biochemical Evidence for Evolution
* Each column should total 146
Table 2 - # of each type of amino acid
Biochemical Evidence for Evolution
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
Domesticated Plants and Animals
Domesticated Plants and Animals
cattle cats
Domesticated Plants and Animals
corn
apples
Domesticated Plants and Animals
Selective (artificial) Breeding
Certificate of Pedigree
Domesticated Plants and AnimalsSelective (artificial) Breeding
Certificate of Pedigree
Certificate of Pedigree
Human (H) Chimp (C)
Chromosome comparison
Human (H)
Chimp (C) Orangutan (O)
Gorilla (G)
Chromosomes of Primates
DNA Base Sequence Comparisons