Download Evolution Evidence and Theory

Evolution
Evidence and
Theory
Chapter 15
Lab Biology
Vocabulary
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Absolute age
Stratum
Fossil
Acquired trait
Relative age
Natural selection
Vestigial
Artificial selection
Coevolution
Adaptive radiation
cast
mold
extinct
law of superposition
adapt
analogous
convergent evolution
divergent evolution
homologous
fitness
Evolution
•A genetic change
within a population
over time!
Fossils
• Fossil is a trace of a long-dead
organism.
– Found:
• 1. Sedimentary rock - formed by dust, sand, or
mud deposited by wind or water over dead
organism
– Usually formed by hard body parts of an organism—
shell, bones, teeth, or woody stems
– Hard minerals replace the tissue of the organism
leaving rocklike structures
Sedimentary Rock
Continue Fossils
2. mold – imprint in rock in the shape
of an organsim
- limestone
3. cast – forms when molds are filled
with hard minerals
Limestone
– Limestone is the most abundant of the non-classic sedimentary rocks.
Limestone is produced from the mineral calcite (calcium carbonate) and
sediment. The main source of limestone is the limy ooze formed in the
ocean. The calcium carbonate can be precipitated from ocean water or
it can be formed from sea creatures that secrete lime such as algae and
coral.
– Chalk is another type of limestone that is made up of very small singlecelled organisms. Chalk is usually white or gray in color.
Cast
• !
Robert Hooke
1635-1703
• He concluded that fossils are remains of
plants and animals
• He mostly studied “petrified wood” with
the aid of the microscope
• He hypothesized that living organisms had
somehow been turned to rock
Petrified Wood
Wood that has turned to stone!
How is Petrified Wood Formed?
• The mud that covered the logs contained
volcanic ash, a key ingredient in the
petrification process. When the volcanic
ash began to decompose it released
chemicals into the water and mud. As the
water seeped into the wood the chemicals
from the volcanic ash reacted to the wood
and formed into quartz crystals. As the
crystals grew over time, the wood became
encased in the crystals which, over
millions of years, turned the wood into
Distribution of Fossils
• Nicolaus Steno (1638-1686)
– “law of superpositon” – states that the top
layers of stratum contain the youngest fossils
while the lower ones are older
• This technique helps scientists to determine the
“relative age” of a fossil
• “absolute age”- age in years determined by
radiological evidence
Succession of Forms
• Mass extinctions – brief periods during
which large numbers of species
disappears.
– Some of these life forms were unlike any
organisms alive today
– Probably resulted from drastic changes in the
environment, volcanic activity or collisions
with asteroids (may have blocked sunlight for
long periods of time and decreased temp.)
Biogeography
• Biogeography – is the study of the
geographical distribution of fossils and of
living organisms.
– A comparison of recently formed fossil types
with types of living organisms in the same
geographic area shows that new organisms
arise in areas where similar forms already
lived.
• Ex: armadillos in North & South America where
glyptodonts lived in the past.
Armadillos
Glyptodonts
Scaphognathus crassirostris
Lab Fossil
Theories of Evolution
• I. Lamarck’s Explanation:
– French scientist (1744-1829)
– Proposed that similar species descended
from a common ancestor (fossil records)
– He hypothesized that acquired traits were
passed on to offspring.
Acquired Trait
• It’s not determined by genes!
• Instead, it arises during an organism’s
lifetime as a result of the organism’s
experience or behavior.
– Ex: 1. webbed foot on water birds resulted
from repeated stretching of the membrane
between the toes
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2. tails – if you don’t use it you loose it!
Beginning of Modern Evolutionary
Theory
• II. Charles Darwin (1809-1882) & Alfred
Wallace (1823-1913)
– “natural selection”-hypothesis that
organisms best suited to their environment
reproduced more successfully than other
organisms
– Darwin & Wallace announced their
hypotheses at the same time
– Darwin’s name became more associated with
evolution The Origin of Species published
Darwin’s Voyage on the Beagle
• Sailed in 1831 for five years
• Collected specimens and kept careful
records of his observations
• Sailed to South America (Galapagos
Islands) and the South Pacific
Darwin’s Findings
• 1. returned to England in October 1836
• 2. collected 13 similar but separate
species of finches.
• 3. Each finch species had a distinctive
bill for specialized food source.
• Implied that the finches shared a recent
common ancestor
Darwin’s Finches
Darwin’s Findings
A GRUB!!!!!!!
• !
Darwin’s Theories
• TWO THEORIES;
– 1. DESCENT WITH MODIFICATION – The
newer forms appearing in the fossil record are
actually the modified descendants of older
species
• Organisms similar to each other come from a
recent common ancestor, organisms that are
more dissimilar such as finches and armadillos
share a more remote ancestor
Continue…
• 2. MODIFICATION BY NATURAL
SELECTION – states HOW evolution
occurs.
– Organisms having traits that make them
better suited for survival tend to leave more
offspring than organisms with fewer beneficial
traits. Darwin called the different degrees of
successful reproduction among organisms in
a population NATURAL SELECTION
Evidence of Evolution
• 1. HOMOLOGOUS STRUCTURES:
similar features that originated in a shared
ancestor
– Similar in structure BUT differ in function!!
– Ex: penguin, bat, alligator, & human (all
derive from the same embryological
structures)
– These examples i.e. share a fairly recent
common ancestor
Homologous Structures
Continue…
• 2. ANALOGOUS STRUCTURES: Similar
functions BUT differ in structure and
embryological development
– Ex: wings of a hummingbird and humming
moth – both can hover to feed
Analogous Structures
Continue…
• 3. Vestigial Structure: Features that
were useful to an ancestor, but they are
not useful to the modern organism that has
them.
– Ex: tailbone in humans, appendix, some
snakes have tiny pelvic bones and limb
bones, some whales have pelvic bones
along with four chambered stomach like a
cow!
Vestigial Structures
Continue…
• 4. Similarities in Embryology
– Ex: all
vertebrate embryos are
similar, but those similarities fade
as development proceeds –
evidence that indicates that
vertebrates share a common
ancestor
Vertebrate Embryos
Continue…
• 5. Similarities in Macromolecules: The
more similar homologous proteins are in
different species, the more closely related
the species are thought to be.
– Ex: the amino acid sequence in human
hemoglobin and gorilla hemoglobin differ
by ONE amino acid
– While the Hb of humans and frogs differ by
67 amino acids!!
Patterns of Evolution
• 1. Coevolution: the change of two or
more species in close association with
each other is called coevolution
– Predators and their prey sometimes co-evolve
• Ex: “tropical region” bats feed on nectar
– Bats have slender muzzle and long tongue that help
them to feed,flowers are light in color which helps bats to
see them at night and have a fruity odor that is attractive
to the bats.
Tropical Bats!
Baby Bats!!
CLOSE UP!!!!
• COOL!
Flowers with Nectar!
Continue…
• 2. Convergent Evolution: occurs when
the environment selects similar
phenotypes, even though the ancestral
types were quite different from each other.
– Analogous structures, such as similiar fins in
very different animals, are associated with
convergent evolution
• Ex: sharks and porpoises
Porpoises
Sharks
Continue…
• 3. Divergent Evolution: two or more
related populations or species become
more and more dissimilar. Divergence is
nearly always a response to differing
habitats and can result in new species
– A) adaptive radiation: many related species
evolve from a single ancestral species ex:
Galapagos finches
– B) artificial selection: all domestic dogs are
the same species “Canis familiaris”
Canis familiaris
• !