Download Topic 04

Bio 1309 Evolution :
an introduction
1
Evolution  the key to
understanding biological diversity


The evolutionary connections explain unity and diversity
of life
Descent with modification accounts for both the unity
and diversity of life.



In many cases, features shared by two species are due to their
descent from a common ancestor.
Differences are due to modifications by natural selection
modifying the ancestral equipment in different environments.
Evolution -- core theme of biology - a unifying thread
2
1
First!
Theory – what does it mean?
A scientific theory is a concept supported by
a broad range of observations,
experiments, and conclusions.
This word is often misunderstood or misused
by the general public…
A theory is NOT a Guess about how
something works…
3
Examples of Theories in Biology
Cell
Homeostasis
Gene
Ecosystem
Evolution
4
2
The Process of Science
A Controlled Study
Experiments in controlled studies have two
types of groups:
Control Group
Experimental Group
5
Evolution- so what about it?

0
Charles Darwin - theory of evolution
by natural selection, his book
presented two important concepts:

Species evolved from ancestors,
and there was modification in
the process or, as Darwin stated,
“descent with modification.”

Natural selection occurs as
heritable variations are exposed
to environmental factors that favor
the reproductive success of
some individuals over others.
6
3
A Shared Discovery?
•Charles Darwin and
Alfred Wallace
developed similar
theories at about the
same timeI guess Charles Darwin had a
better agent!
7
Darwin’s Observations


Individual Variation - Individuals in a population
of any species vary in many heritable traits
Differential reproductive success –



A population can produce more offspring than
environment can support
struggle for existence among variant members of a
population.
inferred  those individuals with traits best suited to
the local environment will generally leave more
surviving, fertile offspring
8
4
Relatives…
9
Natural Selection


Natural selection -- an
editing mechanism
Occurs when populations
(or organisms), with
inherited variations, are
exposed to environmental
factors that favor the
reproductive success of
some individuals over
others
10
5
Struggle for Existence


Struggle for existence: A population produces
many more offspring than can survive long
enough to reproduce. This idea was based on
Thomas Malthus’s Essay on the Principle of
Population – populations tend to increase faster
than their food supply.
This leads to competition and is of great
consequence in differential reproductive
success
11
Natural Selection

Natural selection, by its cumulative effects
over vast spans of time, can produce new
species from ancestral species.



a population may be fragmented into several
isolated populations in different
environments.
What began as one species can gradually
diversify into other species.
Isolated populations adapt over generations
to different environmental problems
12
6
Example: Finches Of The Galapagos Islands

Diversified after an initial colonization from the mainland to exploit
different food sources on different islands.
13
Descent With Modification

accounts for both the unity and diversity of
life


In many cases, common features due to
descent from common ancestor
Differences are due to modifications by
natural selection modifying the ancestral
equipment in different environments.
14
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
7
Adaptation


0
The product of natural
selection is
adaptation, the
collection of favorable
modifications in a
population over time.
All organisms have
adaptations, evolved
through natural
selection
15
Adaptation is NOT:
A trait acquired after birth…
A matter of choice…
16
8
Evolution and Classification
Classification schemes allow for a universal
tree of life “phylogenetic tree”.
Living things change gradually over millions
of years
Changes favoring survival are retained & less
beneficial changes are lost.
17
Nomenclature (revisited)
Binomial (scientific) nomenclature
Genus – Bacillus, always capitalized
species - subtilis, lowercase
Both italicized or underlined
Bacillus subtilis
(B. subtilis)
18
9
Identification and Classification
The process of discovering and recording the
traits (physical, biochemical, genetic) of
organisms, thereby, placing them in a
taxonomic scheme.
19
Some supporting evidence
•
•
•
•
Geologic records (physical information)
Physics observations
Radiation records (measurable data)
Mathematical and biological paradigms:
– Bacterial antibiotic resistance
– Mitochondrial enzymes
– DNA, RNA and protein change rates
Actually the volume of scholarly literature is staggering….
20
10