Download Unit 3 - Section 8.1 Theory of Evolution

Grade 11 University Biology – Unit 3 Evolution
Theory of Evolution
Section 8.1 Page 326-331
Fossils are important to the study of evolution.
 A fossil is the preserved remains of a onceliving organism.
 The study of ancient life through the
examination of fossils is palaeontology.
Fossils of hard mineral parts (like bones and teeth)
were formed by the following process.
 An animal was quickly buried after death (e.g.,
sinking in mud, buried in a sand storm). This
rapid removal from air prevented degradation
by microorganisms or decay by weathering
 Over time, more and more sediment covered
the animal’s body.
 Parts of the animals did not rot (...usually the harder parts like bones and teeth) were encased in
the newly-formed sediment.
 After a long time, the chemicals in the buried animal’s bodies underwent a series of changes. As
the bone slowly decayed, water infused with minerals seeped into the bone and replaced the
chemicals in the bone with rock-like minerals. The process of fossilization involves the dissolving
and replacement of the original minerals in the object with other minerals (and/or
permineralization, the filling up of spaces in fossils with minerals, and/or recrystallization in which
a mineral crystal changes its form). This process results in a heavy, rock-like copy of the original
object (i.e., a fossil). The fossil has the same shape as the original object, but is chemically more
like a rock.
 NOTE: Most animals do not become fossils. They simply decay.
Georges Curvier (1769-1832) is largely credited with developing the science of palaeontology.
 Curvier determined that each layer of rock (stratum) was characterized by a unique group of
fossils AND the older (deeper) the stratum layer, the more dissimilar the species are from
present day life
 Curvier believed that most if not all the animal fossils he examined were remains of species that
were now extinct.
 Curvier proposed the idea of CATASTROPHISM that explained the extinctions or killings of many
species by violent and sudden natural disasters such as volcano eruptions and floods.
Charles Lyell (1797-1875) presented the contrasting idea of UNIFORMITARIANISM. He noted that the
rate of geological change has not changed.
Geological change is slow and continuous.
The rate of change is the same today as it
was 1 million years ago.
Jean-Baptiste Lamarck (1744-1829)
compared the skeletons of modern species
with fossils.
 Lamarck noted that there were “lines
of descent” in which a series of
fossils led to modern species.
 Lamarck offered with the idea that an
organism can pass on characteristics
that it acquired during its lifetime to
its offspring -- known as


INHERITANCE OF ACQUIRED CHARACTERISTICS.
Lamarck proposed that an organism’s adaptations to the environment resulted in characteristics
that could be inherited by offspring. This helped to explain that species could change over time.
NOTE: Lamarck’s idea about inheritance (i.e., inner need) is NOT how the giraffe got its long
neck as proposed in the above illustration).
Lamarck also suggested that body parts not used would eventually disappear ...called USE AND
DISUSE
Charles Darwin (1809-1882) introduced the THEORY OF EVOLUTION BY NATURAL SELECTION – A
theory explaining how life has changed, and continues to change, during Earth’s history. See Table 8.1
on Page 329 to see Darwin’s observation in detail
 Darwin saw organisms that were very
different from organisms in Europe. He
noted geographic groupings. He asked,
“Why is distribution clustered and NOT
random?”
 Darwin observed fossils of extinct
animals were similar to living animals.
 Some organisms in isolated areas (e.g.,
Galapagos Islands) resembled animals
from nearby geographic areas. Darwin
asked, “Why?”
 After observing morphological
differences in the finches of the
Galapagos Islands, Darwin asked, “Why
is there diversity of species in a small
area?”
 Finally, Darwin asked, “Can the
processes of artificial selection occur naturally?” There are now at least 13 species of finches on
the Galapagos Islands, each filling a different niche on different islands. All of them evolved from
one ancestral species which colonized the islands only a few million years ago. This process
whereby species evolve rapidly to exploit empty “eco-space” is known as ADAPTIVE
RADIATION.

Darwin (and Wallace...see below) suggested that individuals with traits that helped them survive
in their local environments were more likely to survive to pass on these traits to offspring.
Competition for limited resources between individuals of the same species would SELECT FOR
individuals with favourable traits (i.e., traits that increased their chances of surviving to
reproduce). Thus, a growing proportion of the population would have these traits in later



generations, and as time passed, the population as a whole would have the traits. This is
SURVIVAL OF THE FITTEST -- organisms that are the fittest leave the most offspring, so those
organisms win the struggle for survival.
These ideas were published in Darwin’s 1859 book The Origin of Species.
Darwin also proposed...
 All life descended from some unknown organisms
 As descendents of an organism spread over different habitats, they developed
adaptations that helped them survive in the new environments
 Organisms produce more offspring than can survive. Thus, organisms compete for
limited resources (e.g., food, shelter)
 Individuals of a population vary extensively, and much of the variation is inheritable
 Individuals that are better suited to local conditions survive more frequently and, as a
result, offspring with the “better” traits are produced
 Processes for change are slow and gradual
Darwin used the phrase DESCENT WITH MODIFICATION. He did not use evolution because it
implies progress. Rather, NATURAL SELECTION does not demonstrate progress. Natural
Selection has not set direction. It is merely results from a species’ ability to survive local
conditions at a specific time and to pass on these traits that helped them survive.
Alfred Russel Wallace (1823-1913) made similar observations to Darwin.
HOMEWORK
 Page 327, Questions 2-6
 Page 331, Questions 1, 5-7, 15