Evolution, Natural Selection and the Diversity of Animals

How do new species begin?

• DNA is instructions for all life

• DNA - RNA Protein Trait

• Mutations MAY cause changes in the production of proteins

• New traits can be passed to offspring– May be helpful, bad or cause no change at all

Mutations• Changes in the DNA sequence of nucleotides:

A’s, G, C’s and T’s– Sickle cell anemia – Harmful? Helpful?– Albinism– Cystic fibrosis– Most diseases and deformities– Blond or brunette– 2 legs or 4 legs?– Fins or flippers?– Color of skin– All differences!

Mutations: the good, the bad, and the indifferent

• Point mutations – one letter change; substitution

• Frame-shift mutations – insertion or deletion of one or more nucleotides that “shifts” information;

• each 3 code for 1 amino acid that makes up a protein• EX: cat ate the ratcatatetherat

• caatatetherat Caa tat eth era t

• Ctatetherat Cta tet her at

• Not all mutations are bad – some make bacteria ANTI-BIOTIC RESISTANT.

Good for the bacteria, not-so-good for you!

• Some mutations result in no change

Mutations can change a population • If new traits is advantageous,

• those w/ trrait will have more successful offspring than those without it

• Over long periods of time…

• populations -- new species• Fish w/ lungs move onto land reptile humans!

• Species = groups that are so similar they can breed with each one another and produce VIABLE (capable of reproducing) offspring.

This is Natural Selection.

New species can develop if…

• Members of a populations are separated from each other (GEOGRAPHIC ISOLATION)

• Members of two populations can no long breed successfully with one another (REPRODUCTIVE ISOLATION)

• Having an abnormal number of chromosomes (POLYPLOIDY)

Divergent Evolution

• One ancestral species leads to 2 new species

Ancestral Green Iguana

Marine Iguana

Land Iguana

Adaptive Radiation

• One ancestral species leads to 3 or more new species

Types of Evolution

Two ideas of how new species develop

• Gradualism: lots of small changes in DNA over long periods of time

• Punctuated Equilibrium: fewer, larger changes over long periods of time.

Gradualism

Punctuated Equilibrium

10 million years

10 million years

Notice the results of both are the same: CHANGE

Evidence for evolution

• Antibiotic resistant bacteria

• Fossils

• Anatomy

• Embryology

• Biochemistry

All of these methods are used together to show relationships between species

Fossil RecordUsed to observe early life:

• Incomplete – only hard parts fossilize in specific types of soil

• Like a puzzle – overall pattern

Anatomy• Similarity in structures

suggests relationships between animal species

• Homolgous and Analogous structures – see diagram

• Vestigial structures – whale pelvis

Homologous and Analogous Structures

• Homologous structures (homo=same) – alike because they are closely relatedExample: bird wings, bat wings, your arm and hand

• Analogous structures (not closely related, but same function)

- -bird wings and

insect wings

Embryology• sperm + egg fertilization zygote (1

cell)

• blastula – about 64 cells

• gastrulation – when blastula begins to fold in– Forms opening into gastrula– gastrula – 2 cells layers = 2 tissue layers

• archenteron – opening into the gastrula

Protostome vs Deuterostome

If the archenteron (opening) forms into:• a mouth first = PROTOSTOME• an anus first = DEUTEROSTOME• All invertebrates (no backbone) are

protostomes except echinoderms• Vertebrates (w/backbone) and echinoderms

= Deuterostomes• Humans?

Living things are grouped according to similarities

• Embryology

The more similar the

embryonic

development pattern the

more closely related

Embryology

Vertebrate embryos share developmental characteristics:– Post anal tails– Pharyngeal slits or pouches– Notochords– Nerve cords

DNA determines these characteristics!

Biochemistry

• All organisms have DNA, ATP, and other enzymes/proteins in common

• DNA is made of 4 molecules: A,T,C, and G

• Similar DNA sequences = similar ancestry

A cladogram is like a family tree showing how things have changed.

Shows relationships based on specific characteristics

Everything to the right of this point have Vertebrae

Point where common ancestors diverged

Living things are grouped according to similarities

• Kingdom• Phylum• Class• Order• Family• Genus • Species

Few similarities Largest # of organisms

Most similarities Smallest # of organisms

Binomial Nomenclature: scientific names are Genus and Species Ex: Iguana iguana, Homo sapien

HOMOLOGOUS structures, humans, birds, porpoises and elephants are considered more closely related to each other than any are to insects.

Living things are grouped according to similarities

Dichotomous keys

• Species can be identified using a dichotomous key

• Series of “either / or” questions leading to the identification.

Dichotomous keys

Example:

1. Does the flower have white or yellow petals?

-if yellow, it is a sunflower

-if white, go to question 2

2. Does the flower have a yellow or red center?

-if yellow, it is a daisy

-if red, go to question 3