Biology Unit 4

Evidence that all tetrapods share a common ancestor

1-2-wrist-5 arm structure, absence of species until the in between forms, homologous structures

Morphological divergence

A macro evolutionary pattern of a change from the body form of a common ancestor. (tied to homologous structures)

Analogous structures

Body parts that look alike in different lineages but did not evolve in a shared ancestor, they evolved separately after the lineages diverged. (tied to morphological convergence)

Convergent evolution vs. divergent evolution

Convergent evolution is when two species with no history of sharing a common ancestor develop similar body traits. Divergent evolution is when a similar body part of two species who shared a common ancestor diverges so that it is dramatically different and sometimes shows no relation to the original body part, but there is still an underlying aspect that shows that the trait is the same/ from the same ancestor..

Chemical features of DNA in gel electrophoresis

DNA's negative charge allows the fragments to travel through the gel towards the positive side, which helps them gather in bands and move down the gel.

Morphological convergence

Evolution of similar body parts in different lineages. (tied to analogous structures)

Major anatomical features that define humans as primates

Large brain relative to body size, Big toe in line with other toes, forward facing eyes (3D depth perception views-good distance judging), Teeth (molars, different teeth for different foods), clavicle/collarbone (wide rang of movement), Hands and feet (fingerprints for grip, nails not claws), Opposable thumbs (for gripping)

Restriction enzymes and biotechnology

Researchers use restriction enzymes to cut DNA from different sources into fragments. Fragments with identical sticky ends are mixed together, and matching sticky ends base pair together, regardless of their origin. DNA ligase seals them together, and that makes recombinant DNA. This is also the first step in DNA cloning. They also use them when DNA fingerprinting.

Chemical features of DNA in DNA extraction

SDS is polar and nonpolar, so are the phospholipids in the cell membrane, so the cell membrane dissolves and releases the DNA. DNA is non soluble in alcohol.

Homologous structures

Similar body parts that reflect shared ancestry. If a species has homologous structures with another species, you know that the reason is because they descended from a common ancestor. (tied to morphological divergence)

Example of divergent evolution (morphological divergence)

Starting with a stem reptile, many different species evolved. The foot, or leg of the stem reptile evolved to be a human hand, all the way to a penguin's, elephant's, and even pterosaurs'. this shows divergent evolution because from the same thing came many different forms of it , that are almost unrecognizable as being related, but you can tell that they shared a common ancestor. These are homologous structures because they evolved from a shared ancestor

Biomolecules and evolutionary relationships

The more recently a species diverged, then the less neutral mutations it will have in its DNA, and Vice versa, Therefore, by looking at the mutations in DNA, you can see how recently a lineage diverged. Also, some essential genes have evolved very little (cytochrome b). Therefore, they have changed very little. Comparisons of proteins' primary structure (order of amino acids) is also used to determine evolutionary relationships. Two species with many identical proteins are likely to be close relatives, and vice versa. If a change in the amino acid sequence is not redundant and changes the phenotype, then it is known as a nonconservative substitution.

Example of convergent evolution (morphological convergence)

Wings of bats, birds and insects are an example of convergent evolution. Each of these species split into a separate lineage, and independently, with no relation to any common ancestor they may or may not have shared, they developed wings. These wings are analogous structures because similar body parts evolved from separate lineages. This represents convergent evolution because similar body traits evolved with no pressure/ influence from a common ancestor.

Major behavioral features that define humans as primates

use of tools, communication, things like burying dead, bipedality, spending less time in trees.

Tetrapod

4 legs

Trends in hominid evolution

As time went on, brain size increased, Hips got shorter and wrapped around the body for better walking, teeth changed to accommodate diets, We started to walk, started to talk, skull shape changed (foreheads, eyebrows, chins), we developed nails and opposable thumbs.

DNA gel electrophoresis in DNA fingerprinting

The tandem repeats can be used to see genetic differences and similarities between individuals, so using electrophoresis on a isolated region of the chromosome, the tandem repeats form bands when they move through it. This results in a band pattern, which shows your DNA. (The size and amount of tandem repeats are unique to an individual, which means that the size of the band will be unique).

Disagreements about human evolution

There is not a consensus among scientists about the exact relationships within the human evolutionary tree because there is no way to be certain. We are discovering new things all the time and things could change with a new discovery. There are also different possibilities, and since there is no way to be sure what really happened, there can't be a definite answer.

Restriction enzymes

These were originally found in bacteria, and were/are used to that bacteriophage didn't have a chance to integrate into the bacterial chromosome. They restrict bacteriophage growth by chopping it up. Restriction enzymes cuts the DNA wherever a specific nucleotide sequence occurs. They often leave "sticky ends", which are single stranded tails on DNA fragments that can base pair together.