Download Diversity and Change over Timemodified

Diversity and Change
over Time
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Please place homework in the basket.
Pick up notes.
Be ready for Testprep questions.
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There are millions of different organisms that
live on the Earth
They vary in size, shape, color
Atelopus frog found in
rain forest of South
America
They vary in…..
• habitat (environmental conditions in
which they can survive)
• how they obtain energy, the method
of reproduction, and lifespan
•All this variation is known as the
diversity of life
E.coli
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Fossil records indicate there are other
organisms that existed in the past
Some fossils are similar to creatures found
today, but others are very different
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Variation occurs within the
same species.
Individuals of the same
species living together are
referred to as a population
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In every population variation exists within the
inherited traits of the individuals
An organism’s phenotype may influence its
ability to find, obtain, or utilize resources
(food, water, shelter, oxygen) and may affect
the organism’s ability to reproduce
Phenotypic variation is controlled by genotype
and environmental influences
Despite all of the variation, there are some
similarities between all living things
1) All living things have nucleic acids (DNA/
RNA)
2) All living things use the same 20 amino acids
to make proteins
3)Transcription and translation occur in all life
forms on Earth
4)All organisms pass genetic information to
offspring through reproduction
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Also, recall that all
organisms are made
of cells and that
cells come from
other cells (life
arises from other
life)
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Charles Darwin made observations that led
him to devise an explanation for the diversity
of life, how living things are related, and how
life changes over time
Darwin made many of his observations while
traveling on a ship , the H.M.S. Beagle
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Charles Darwin was born on the same day as
Abraham Lincoln, Feb 12, 1809
He came from a family of doctors
When Charles started medical school, he found he did
not like it
He went to theological school to become a minister
He had an interest in nature and also took courses in
biology and geology
He accepted a 5 year job on the H.M.S. Beagle where
he worked as a naturalist and was an educated
companion for the captain
Darwin Left England in 1831
Darwin returned 5 years later in 1836
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One place he visited was the
Galapagos islands located
west of South America
The islands are close
together, but have different
climates and thus a different
environment
Small brown birds (finches)
living on the islands were
similar, but had very
different beaks
Tortoises were similar, but
had different shell shapes
Ideas that Shaped Darwin’s
Thinking
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Darwin lived in a time when explorers were
traveling the world and challenging long-held
views about the natural world
The old views were that the Earth and all life
were only a few thousand years old and that
neither the planet nor life had changed through
time
Theories of Geologic Change
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Geologists in Darwin’s time began suggesting
that the earth was much older.
James Hutton proposed that the Earth is
shaped by geological forces that take place
over millions of years (gradualism)
Charles Lyell stressed that past geological
processes are the same processes that continue
to shape the Earth today (uniformitarianism)
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Examples of geologic processes are:
Erosion (such as water carving out mountains
forming canyons)
Underwater Volcanoes erupt and release lava
that can form islands
Earthquakes cause land to be lifted up and
form mountaintops
These processes helped shape the Earth over
millions of years, and we can continue to
observe them today
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Darwin asked: If the Earth can change over
time, can life change as well?
If the earth was extremely old then it allowed
for a great deal of time for life to change
Malthus
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Thomas Malthus was an economist who
published a book about population growth
He proposed that resources are limited and that
if the human population continued to grow
without limits that eventually food and space
would be insufficient
Darwin applied this concept not only to
humans, but to all living things
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He reasoned that if all offspring from every organism
survived, that they would overrun the world
This hasn’t happened because most of the offspring
die, and of those that live, not all are successful in
reproducing
Darwin wondered what caused so many deaths and
what factors contributed to survival and reproduction
These questions became central to Darwin’s
explanation of evolutionary change
Lamarck
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Jean-Baptiste Lamarck was one of the first
scientists to believe that change over time
occurred in populations.
Lamarck’s method of how evolution occurred
was flawed, but he paved the way for future
scientists such as Darwin
Lamarck
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Lamarck’s idea involved the “inheritance of acquired
traits”. This meant that changes in an individual that
occurred during their lifetime would be passed on to
their offspring
He felt that if an organism used or did not use a
particular body part, that the part would be enhanced
or eliminated in the offspring (the law of use and
disuse)
Example, if you work out and build big muscles, your
children will have big muscles
Giraffes who stretch their necks to get higher leaves
will have offspring with longer necks
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Lamarck
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For example, birds developed wings by trying
to use their front limbs for flying and then
passing on the “improved” limbs to their
offspring
If wings were not used, then wings would
decrease in size until they were lost altogether
Problem with Lamarck’s Theory
Darwin’s Findings
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In 1859, Darwin published the results of his
work and observations his book called “On the
Origin of Species”
He presented the mechanism for evolution
known as natural selection and included that
evolution has been taking place over millions
of years and continues in all living things
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In Darwin’s time, genetics was not yet
understood, but it was clear that variation
existed within a population
For example:
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some cows gave more milk than others, some
strawberry plants gave larger strawberries
Humans then selectively bred the organisms to
achieve desired traits
Darwin called this “artificial selection”
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Natural selection was based on the “survival
of the fittest” in nature
The struggle for existence relates back to
Malthus’s overpopulation problem. It means
that each individual competes for food, space,
and resources
Those who are better able to compete, obtain
the resources, and are more likely to survive
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The better suited an organism is to its
environment, the greater the chance of survival
is
Fitness is the ability of an individual to
survive and reproduce in its environment
More “fit” individuals are more likely to
survive
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Adaptations are any inherited characteristic
that increases survival
Adaptations can be in the anatomy of the
individual or in it’s behavior.
Think of examples of adaptations…
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Birds build nests to protect their eggs
Wolves hunt in packs
Walking leaf insect
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http://videos.howstuffworks.com/discovery/28
313-dirty-jobs-malaysian-walking-leaf-insectvideo.htm
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As more “fit” individuals out-survive and outreproduce less “fit” individuals, certain traits
increase over time
Over time the population changes (just as in
artificial selection) and these changes increase
a species’ fitness in its environment
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Given enough time, natural selection will
produce organisms that have different physical
characteristics and occupy different habitats
than their ancestors
Though related, these new organisms are
somewhat different than the species from
which they came from
Darwin termed this principle as “descent with
modification”
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Please pick up a copy of the notes.
Be prepared to answer the Testprep questions.
Quiz next class session on Evolutionary
Theory.
Evidence used to by Some
Biologists to Support
Evolutionary Theory
Evidence for evolution is sited by evolutionists
in these scientific fields:
 Paleontology
 Anatomy
 Embryology
 Biochemistry
Paleontology/Fossil Record
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By comparing fossils from older rock layers
with fossils from younger rock layers,
evolutionists believe the fossil record provides
evidence of change in life forms along a
timeline
Transitional fossils are fossils that show links
in traits between groups of organisms and are
used to show intermediate stages of evolution
of a species
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Even though millions of fossils have been
discovered, many environmental conditions
must be met in order for a fossil to form
Fossils are more likely to be found for species
that existed for a long time, were abundant and
widespread, and had hard shells or skeletons
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It is rare that an organism will form a fossil, so gaps
in the fossil record occur when intermediate fossils
have not yet been discovered
These gaps are sometimes referred to as “missing
links”
As more and more fossils are discovered, the gaps are
filled and the understanding of how particular species
evolved increases
Fossil Distribution
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Law of superposition was proposed by Nicolaus
Steno in 1669.
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States that successive layers of rock and soil were
deposited on top of one another with wind and water. The
oldest stratum (or layer) is on the bottom and newest is on
top.
This law has been used to give relative age to fossils. (the
age of a fossil compared to another fossil-younger or
older).
Absolute age can be determined through radioactive
dating.
Radioactive Dating
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Radioactive Dating – Technique used to
establish the age materials.
Atoms of the same element but differ in the
number of neutrons are isotopes.
Radioactive Dating
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Certain isotopes (radioactive isotopes) have unstable
nuclei that may undergo radioactive decay.
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The nucleus releases particles or radiation or both causing
the isotope to decay.
One example is carbon. Carbon exists as both Carbon-12
and Carbon-14 (12 and 14 denote the mass number (the
total number of protons and neutrons).
Carbon-14 undergoes radioactive decay while carbon-12
does not.
Radioactive Dating
Cont…..
 Living things constantly take carbon in and the
ration of carbon-14 to carbon-12 is a known
quantity.
 After death, production of carbon halts and the
decay of carbon-14 begins.
 Overtime carbon-14 decays with respect to the
stable carbon-12.
Radioactive Dating
Cont…
 After 5,730 years, half of the carbon-14 present in the
organism will have decayed. Therefore the half-life of
carbon-14 is 5730 years.
 Carbon dating is limited to materials that are less than
60,000 years old.
 Other isotopes that might be used:
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Thorium-230
Potassium-40
Uranium-238
Half life 75,000
Half life 1,300,000,000
Half life 4,500,000,000
Anatomy/Homologous Body
Structures
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Anatomy is the study of structures of
organisms
To the evolutionist, the greater the number of
shared structures between species, the more
closely the species are related
Structures that have different mature forms,
but that develop from the same embryonic
tissue are called homologous
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An example of homologous structures are the
forelimbs of different creatures
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Vestigial organs- are structures with little or no
apparent function to the organism.
Evolutionists believe these are remnants of
structures that existed in their ancestors.
Common examples that are often sited are the
appendix and the tail bone.
Often vestigial organs of one species are
homologous with structures in a related species
in which the structure has remained functional
Anatomy and Geographic
Distribution
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Species located in different geographical
locations reveals that species in different
locations, but under similar ecological
conditions developed similar structures and
behaviors
Structures that have a similar function, but
different evolutionary origins are known as
analogous to evolutionists.
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If a species encountered a different
environment due to a change in geographical
location, different adaptations were favored
This could eventually lead to a new species
with a shared common ancestor to the original
population
Embryology
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The study of how an embryo develops is a
field called embryology
Sometimes similarities in the patterns of
development of structures that are not obvious
in adult organisms become evident when
embryonic development is observed
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The embryos of vertebrates are very similar in
appearance early in development, though they grow
into different adult structures
Cells develop in the same order and in similar
patterns to produce tissues and organs of all
vertebrates
These common cells and tissues will produce
homologous structures
Similarities in embryonic develop are believed by
evolutionists to support that these species evolved
from common ancestors
Biochemistry
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The study of chemical processes examines genes and
proteins
The more similar the DNA of two species, the more
likely they are to be related
Looking at DNA evidence has been very helpful
when studying relationships that are not easy based
on physical characteristics
Examples: if species are very closely related and
share many structures
Or if species are so diverse that they have a lot of
variation in structures