Transcript Notes: Natural Selection, Evolution, and the Development of Animals

Sponges, Jellyfish and…us
The evolution of animals
Where do new species come
from?
• All living organisms have instructions
• DNA and RNA
• mutations in DNA or RNA can cause
changes in the manufacture of proteins
Mutations
changes in protein synthesis can change the
way an organism appears:
• sickle cell anemia
• albinism
Mutations: the good, the bad, and the
indifferent
• Point mutations
• Frame-shift mutations
• 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 are changes in DNA
• Changes in DNA result in changes in the
protein.
• Changes in the protein can introduce new
characteristics (blonde hair)
• New traits can be passed to offspring
Mutations can change a population
• If new traits are advantageous, those
individuals will have more offspring with the
new traits (sickle cell).
• Over long periods of time, these populations
can become new species.
• Species are defined as groups that can breed
with each other and produce VIABLE
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 stop breeding
with each other (REPRODUCTIVE
ISOLATION)
• Having an abnormal number of chromosomes
(POLYPLOIDY)
Divergent Evolution
• One ancestral species leads to 2 new species
Marine
Iguana
Land
Iguana
Ancestral
Green Iguana
Adaptive Radiation
• One ancestral species leads to 3 or more new
species
Gradualism or Punctuated
Equilibrium?
• 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
10 million years
Punctuated Equilibrium
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 to
show relationshipsbetween species
Fossil Record
Used like a puzzle 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
• Vestigial structures – whale pelvis
Homologous and Analogous
Structures
• Homologous structures (homo=same) VS
Analogous structures (not the same, but same
function)
- bird wings and
bat wings
-bird wings and
insect wings
Embryology
•
•
•
•
sperm + egg
fertilization
zygote
blastula – about 64 cells
gastrulation – folds in like a deflating
basketball
• gastrula – 2 layer
• archenteron – opening of the gastrula
Living things are grouped
according to similarities
• Embryology
Organisms that have
similar embryonic
development are more
closely related
Embryology
Vertebrate embryos share developmental
characteristics:
• Post anal tails
• Pharyngeal pouches
• Notochords
• Nreve cords
DNA determines what these develop into
Protostome vs Deuterostome
If the archenteron forms into a mouth first =
PROTOSTOME
• Almost all invertebrates (echinoderms are
the exception)
Protostome vs Deuterostome
If the archenteron develops into an anus first=
DEUTEROSTOME
• Echinoderms and all vertebrates
Biochemistry
• All organisms have DNA, ATP, and other
enzymes
• DNA is made of 4 molecules: A,T,C, and G
• Similar sequences = similar ancestry
A cladogram is like a family tree
showing how things have changed.
Shows
relationships
based on
specific
characteristics
Point
where
common
ancestors
diverged
Everything to the
right of this point
have Vertebrae
Living things are grouped according to
similarities
•
•
•
•
•
•
•
Kingdom
Phylum
Class
Order
Family
Genus
Species
Largest
Smallest
Binomial Nomenclature: scientific names are Genus and
Species
Ex. Iguana iguana
Living things are grouped according
to similarities
With
HOMOLOGOUS
structures,
humans, birds,
porpoises and
elephants are
considered more
closely related to
each other than
any are to insects.
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