Download Natural Selection

Biology Guided Notes
Evolution
Fossil:
Help identify how ecosystems and org. have evolved and changed
Formation:
1. org. is buried in sediment soon after it dies
2. sediments build up & stop decay
3. depending on conditions so portions of the org. may be
preserved or may transform into rock
Types:
1. Trace: indirect evidence
2. Casts: minerals fill in space left by org. after is decays
3. Molds:
4. Petrified: minerals have replaced hard parts of org.
5. Amber/Frozen: Org. is quickly encased in sap or flash frozen
What can fossils tell us?
e.g.-T-rex used big tail for balance
-footprints show behavior patterns, speed, & relationships to other
org.
-sediments help tell when org. lived & what the env. was like
-fossils found in groups show behavior patterns & relationships to
other org.
-help create Geologic Time Scale-
Determining Fossil Age
-helps create fossil record (history of life)
1. Relative Dating:
Interpretation for relative dating
-Correlation: matching rock layers in different areas to show
geographic & organic evolution (in a specific region)
-Index fossil: org. that appeared over wide ranges
-allows for relative dating between different regions
-e.g. Trilobites
2. Absolute dating: provides an accurate age
-Radiometric dating:
-By measuring the ratio of isotopes/
elements in the rocks
surrounding a fossil, its age
can be determined.
-Carbon-14 is used for organic fossils
-half-life =
-it decays into Nitrogen-14
-Uranium-238 (half-life = 4.46 billion years) or Potassium-40
(half-life = 1.27 billions years) are used for older fossils
-must be tested on igneous (volcanic) rock that is in the
same layer as the fossil
Evolution & Natural Selection
Evolution:
-doesn’t have to create a new species, may modify a population
Macroevolution:
Microevolution:
-changes in the genetic equilibrium
of a population based on
differential reproduction
1809- J. B. de Lamarck
-believed species aren’t constant, they evolve from pre-existing
species
-evolution involved 2 principles
1. Law of Use & Disuse
2. Inheritance of Acquired Characteristics
-e.g. giraffe’s
-theory incorrect because inheritance of DNA isn’t affected by
acquired characteristics
Charles Darwin:
-boarded HMS Beagle in 1831 as a naturalist on 5 year round-theworld trip
-collected org., rocks, & fossils
-most information collected from Galapagos Islands (finches,
tortoises, & marine iguanas)
-Bred pigeons to demonstrate artificial selection:
Natural Selection:
-based on which org. can survive and reproduce more successfully
-survival of the “fittest” (best about to reproduce)
Thomas Malthus: found that populations tend to grown geometrically
(2,4,8,16,32), but food supply grow arithmetically (1,2,3,4)
-
-Darwin used Malthus’ ideas to help create the idea of natural
selection
-Coauthored paper with Alfred Russell Wallace who was working
on natural selection at the same time. Darwin reported his
findings first.
6 main points of Darwin’s theory
A. Overproduction:
B. Competition: species must compete for resources, not all
survive
C. Variation: differences in characteristics of inds. in a species
-variations that increase survival are passed on
D. Adaptations:
E. Natural Selection:
F. Speciation:
-over generations, adaptations accumulate & result in new
species
e.g. Giraffes
-some had longer necks & could reach food unavailable to
others
-as env. changed & grass disappeared those who could
reach leaves on trees survived & passed on trait
Evidences of Evolution
A. Fossils
-
-determining age and environment helps link related org. and show
change over time (precursors)
B. “Living Fossils”
-helps link current and past org.
-provides understanding of successful adaptations
C. Structural Adaptations
-e.g. Darwin’s Finches
D. Mimicry
-one species resembles another
OR
E. Camouflage
-enables species to blend into its surroundings
-
F. Physiological adaptations
-Causes:
-drug-resistant strains of bacteria & viruses
-need for a new flu vaccine every year
-chemical-resistant species of insects & weeds
G. Homologous Structures:
-
-Shows phylogenetic relationship
(phylogeny)
H. Analogous Structures:
-Shows how the environment can
“select” orgs. with specific
adaptations to be most
successful (natural selection)
I. Vestigial Structures:
-may have developed into something else, or may be nonfunctional
-
J. Embryology:
-Scientists look for similarities
-e.g. tail, pharyngeal (gill) pouches
-Haeckel’s recapitulation theory
-Ontogeny recapitulates phylogeny
K. Biochemistry
-
Mechanisms of Evolution
Populations evolve
-evolution is a change in the genetic make-up of a population over
time
-Some genes are more successful (cause org. to survive &
reproduce better)
-Gene pool:
-Allelic frequency: % of a specific allele in the gene pool
-Genetic equilibrium:
-mutations cause new genes/alleles/phenotypes to appear in
a population
-many are lethal and quickly eliminated
-some have no effect
-those that are beneficial will be passed on
Gene flow
-can change the allelic frequency
-immigration:
-emigration:
Genetic drift:
-occur in small, isolated populations that have become separated
from their original gene pool
-new pop. gene pool is different from original
-Adaptive radiation:
-variations within the pop. cause different ind. to be better adapted
to one habitat
-causes several species to form at the same time from the original
pop.
Patterns of Evolution
____________________________: species that were similar (or from
the same ancestor) become different due to isolation, adaptation,
& natural selection
Convergent Evolution:
-analogous structures
___________________: idea the species
gradually change over time due to
accumulated adaptations & changes in
allelic frequencies
Punctuated equilibrium: