Transcript Evolution Cont`d

Evolution Cont’d
http://www.buildamovement.com/blog/wpcontent/uploads/2009/09/evolution.jpg
7th Grade Biology
Mr. Joanides
The Fossil Record
• Fossil – Preserved remains or markings left by
organisms that live in the past.
– Most fossils are found in sedimentary rock
– Others can be buried under volcanic ash and dust
• Sedimentary rock – eroded particles of sand,
silt, etc that flow down river to seas and
swamps and settle at the bottom. Over time,
they are cemented together under pressure
and heat to form rock.
Sedimentary Rock Being Formed
http://geoscape.nrcan.g
c.ca/nsask/images/rock
s1_e.jpg
The Fossil Record
• Provides evidence of Earth’s changing life.
• Ex. Timelines from class
• Earth is 4.6 billion years old (byo)
• Oldest known fossil is 3.8 byo.
• Fossils of prokaryotes [bacteria and archaea]
3.5 byo (oldest form of life)
• Fossils in younger rock show evidence of
evolution
Evolution of the Whale
• Modern whales evolved 50 million years ago…
• But from where?
– Fossils of extinct species can help put the puzzle
together.
– Basilosaurus
http://upload.wikimedia.org
/wikipedia/commons/archiv
e/4/4e/20080706155500!Ba
silosaurus.jpg
Geographic Distribution
• Differences and similarities between
organisms around the world
– Evolved from ancestral forms
TOPIC FOR DISCUSSION
• Why do S. American tropical species have
more in common with S. American desert
species than they do with African desert
species?
Australia…Unique Plants and
Animals
• Numerous pouched mammals (marsupials)
• Few placental mammals
• Why did this happen?
• Also…a good case study for introduced
animals…economic and ecologic nuisances
http://www.camelotbears.com/images/koala_baby_pic.jpg
Homologous Structures
• Forelimbs of animals & goose bumps
http://www.thisviewoflife.org/evolution/forelimb%20homologies.jpg
Vestigial Structures
• Modern whales have no hind limbs, but still
have remnant hipbones
http://www.answersingenesis.org/home/area/magazines/tj/images/v14n2_vestigial_structures.gif
Definitions
• Homologous structures – structural
similarities species share from a common
ancestor
• Vestigial structures – are remnants of
structures that may have had important
functions in an ancestral species, but have no
clear function in modern descendant.
Similarities in Development
• Embryos of closely related organisms have similar
states in development.
http://home.honolulu.hawaii.edu/~pine/book1qts/embryo-compare.jpg
Genetics
• DNA & Protein analysis are new tools for
testing evolution
• DNA passed from parents to offspring, so
should show evolution (i.e. ancestry)
• Darwin hypothesized that all life forms are
related. He was right and it is proven in the
fact that DNA is the common language in
which traits are passed.
Hemoglobin Comparisons
http://www.txtwriter.com/Backgrounders/graphics/evolution/page13.jpg
Answer these in your notes (5 min)
• Why are older fossils generally in deeper rock
layers than younger fossils?
• How can evolutionary theory explain why
Australia is home to relatively few native
placental mammals?
• What are homologous and vestigial
structures?
• What can you infer about species that differ
significantly in their DNA sequences?
Natural Selection
• Population – a group of individuals of the
same species living in the same area.
• “Survival of the Fittest”
http://www.truthinscience.org.uk/site/image
s/stories/peppered%20moth.jpg
Artificial Selection
• Definition – Selective breeding of
domesticated plants and animals to produce
offspring with genetic traits that humans
value.
– Chickens that weigh too much
– Dogs with aggression
– Dogs with keen sense of smell and longing to
retrieve
– Plants that are not susceptible to pesticides
Pesticides – Natural Selection in
Action
• Pesticides are poisons used to kill pests
– Insecticides
– Rodenticides
– Etc
• A little poison will kill 99% of “pests” the first
time
• Second time it’s not as successful. Why?
Inherited Resistance
http://upload.wikimedia.org/wikipedia/commons/thumb/8/85/Pesticide_resistance.svg/57
3px-Pesticide_resistance.svg.png
Affects of Pesticides
• Birth
Defects
• Cancer
• Stronger
Resistance
• Affects
Native
Species
http://water.usgs.gov/nawqa/pnsp/pubs/fs1
52-95/atmos1.gif
Gene Pools
• Consist of all the alleles (genes) in all the
individuals that make up a population.
http://www.visschervisi
ons.com/Dogs/group_
pic.jpg
Changes in Gene Pools
• Mutations
• Sexual recombination
– Promotes survival and reproductive success
– Some alleles become more common
• Ex. Peppered Moth
• Microevolution – A generation-to-generation
change (over a short time)
Genetic Drift
• A change in the gene pool of a population due
to chance.
– Occurs more drastically in smaller populations
• Ex. Coin toss
• 10 x’s vs 1,000 x’s
• The Bottleneck Effect – Disasters such as
earthquakes, floods, droughts and fires may
drastically reduce the size of a population,
which reduces the size of its gene pool.
Bottleneck Effect
http://www.kminot.com/art/charts/bottlenec
k_effect.jpg
http://www.gumballmachine.com/imgs/b
ulk/zj505_red_g_fron
t_01.jpg
Mutations
• Change in the DNA of an individual, which in
turn can change a population over great time.
• Influenced by natural selection or genetic
drift.
• Darwinian fitness = the contribution that an
individual makes to the gene pool of the next
generation.
Interesting Mutations
• Sickle cell disease
• Antibiotics and Bacterial Resistance
– Tuberculosis
http://www.biojobblog.com/Bacteria.jpg
Interesting Mutations cont’d
http://news.softpedia.com/images/news2 http://blog.media-freaks.com/wp/Researchers-discover-how-to-detect- content/uploads/2009/04/teenage-mutantmutations-2.jpg
ninja-turtles.jpg