BSC 2010 - Exam I Lectures and Text Pages
• I. Intro to Biology (2-29)
• II. Chemistry of Life
–
Chemistry review (30-46)
–
Water (47-57)
–
Carbon (58-67)
–
Macromolecules (68-91)
• III. Cells and Membranes
–
Cell structure (92-123)
–
Membranes (124-140)
• IV. Introductory Biochemistry
–
Energy and Metabolism (141-159)
–
Cellular Respiration (160-180)
–
Photosynthesis (181-200)
Evolution and Adaptation: Properties of Life
• Evolution accounts for life’s unity and diversity
• The history of life
– Is a saga of a changing Earth billions of years old
Figure 1.17
Evolution and Adaptation: Properties of Life
3 basic themes:
1) variation: in the genetic makeup of
individuals
2) adaptation: of traits to the environment
3) natural selection: leads to differential
reproduction: those organisms better
adapted produce more offspring
The evolutionary view of life
– Came into sharp focus
in 1859 when Charles
Darwin published On
the Origin of Species by
Natural Selection
– He described the theory
of natural selection.
Prior to this, many
scientists and scholars
believed in evolution,
but there was no solid
idea about how it
worked.
Figure 1.18
The Origin of Species articulated two main points
– Descent with
modification
– Natural selection
Figure 1.19
Theory of Natural Selection:
requires 3 basic conditions:
• 1. Individuals vary (all organisms are not
equal)
• 2. There is a struggle for limited resources (i.e.
competition)
• 3. Organisms have differential success at
reproduction.
Evolution and Adaptation are key features of
life. Evolution provides evidence that life
responds to changes in the environment.
He proposed “Natural Selection”
As the mechanism for evolutionary adaptation of
populations to their environments
Population
of organisms
Hereditary
variations
Overproduction
and struggle for
existence
Differences in
reproductive success
Figure 1.20
Evolution of adaptations
in the population
Natural selection is the evolutionary process that occurs
– When a population’s heritable variations are exposed
to environmental factors that favor the reproductive
success of some individuals over others
1
Populations with varied inherited traits
2 Elimination of individuals with certain traits.
3 Reproduction of survivors.
Figure 1.21
4 Increasing frequency of traits that enhance
survival and reproductive success.
The products of natural selection
Are often exquisite adaptations of organisms to
the special circumstances of their way of life
and their environment
Figure 1.22
• Evolution is change over time within the original gene pool.
• It is possible to have change through random mutations, without
natural selection, but usually it is beneficial mutations that are
enhanced through natural selection: Some mutations confer
adaptive value.
• Example: A mutation may have the effect of allowing a bacterium to
survive or resist a bacterial spray or an antibiotic. That bacterium
survives, and produces offspring, passing on the resistance
mutation, so in the next generation more of the bacteria are
resistant. Thus a resistant strain of bacteria evolves, and soon we
find it more and more difficult to eliminate harmful bacteria.
• So, a mutation can create variation on which natural selection then
acts. The environment itself does not create change.
Natural selection leads to greater reproduction of well-adapted
individuals, which leads to evolution (change in gene frequency
over time).
The Tree of Life
• Many related organisms
– Have very similar anatomical features, adapted
for their specific ways of life
• Such examples of kinship
– Connect life’s “unity in diversity” to Darwin’s
concept of “descent with modification”
Darwin proposed that natural selection
Could enable an ancestral species to “split” into two or
more descendant species, resulting in a “tree of life”
Large
ground finch
Large cactus
ground finch
Small
ground
finch
Large
tree finch
Camarhynchus
Green
Geospiza
Gray
Geospiza
magnirostris
psitacula
warbler
warbler
Sharp-beaked
fuliginosa
Woodpecker Medium
Geospiza Medium
finch
finch
tree
finch
ground finch
finch
conirostris ground
finch
Certhidea Certhidea
GeospizaCactus
Cactospiza Camarhynchus olivacea fusca
difficilis ground finch
pauper
pallida
Geospiza Mangrove
Small tree finch
finch
fortis
Geospiza
Camarhynchus
Cactospiza
scandens
parvulus
heliobates
Vegetarian
Cactus flower
Seed eater
Seed eater
finch
eater
Platyspiza
crassirostris
Insect eaters
Ground finches
Figure 1.23
Tree finches
Bud eater
Warbler finches
Common ancestor from
South American mainland
Each species is a twig on a branching tree of life
– Extending back in time through ancestral
species more and more remote
• All of life
– Is connected through its long evolutionary
history
Evolution: is a change in gene frequency over time.
• It is the result of two main processes:
1. natural selection: “survival of the fittest”. Some organisms,
due to the characteristics of their environment, will survive and
reproduce more than others. e.g. Galapagos finches- some had
larger beaks than others when a drought hit the islands, leaving
only thick, hard seeds. Only the birds with large beaks were able to
eat, the others starved. Therefore, the big-beaked birds had the
energy to reproduce and the next generation all had large beaks.
2. adaptation: the process of becoming better suited to the
environment. Can happen through natural selection or through
genetic drift (random change due to mutation or circumstances).
• * The word “adaptation” can also be used to describe a trait of
a particular organism that has arisen through natural
selection. e.g. a giraffe’s long neck is an adaptation for eating
leaves of tall trees.
Eleven themes that unify biology
Table 1.1
BSC 2010 - Exam I Lectures and Text Pages
• I. Intro to Biology (2-29)
• II. Chemistry of Life
–
Chemistry review (30-46)
–
Water (47-57)
–
Carbon (58-67)
–
Macromolecules (68-91)
• III. Cells and Membranes
–
Cell structure (92-123)
–
Membranes (124-140)
• IV. Introductory Biochemistry
–
Energy and Metabolism (141-159)
–
Cellular Respiration (160-180)
–
Photosynthesis (181-200)
Chemical Foundations of Biology
An understanding of the workings of the cell and the
physiology of multicellular organisms requires an
understanding of chemistry.
Living organisms are chemical systems.
• The bombardier beetle uses chemistry to
defend itself
Figure 2.1
Matter, Elements, Molecules, Compounds
Matter consists of chemical elements in pure form
and in combinations called compounds
Organisms are composed of matter, which is
anything that takes up space and has mass.
Element: basic unit of matter, cannot be
subdivided into simpler substances (by ordinary
chemical means). The smallest unit of an element
is a single atom.
Molecule: a substance composed of more than
one atom.
• A compound
– Is a substance consisting of two or more
elements combined in a fixed ratio
– Has characteristics different from those of its
elements
+
Figure 2.2
Sodium
Chloride
Sodium Chloride
Matter
• All matter is made up from 92 naturally
occurring elements.
• Living matter requires only 25 of these 92
elements. These are the “Essential
Elements of Life”.
Essential Elements of Life
Carbon, hydrogen, oxygen, and nitrogen
(CHON) account for 96% of living matter.
A few other elements make up the remaining 4%.
• Trace elements
– Are required by
an organism in
only minute
quantities
The effects of essential element deficiencies
Figure 2.3
(a) Nitrogen deficiency
(b) Iodine deficiency
Element’s properties depend on structure of its atoms
• Each element
– Consists of a certain kind of atom that is
different from those of other elements
• An atom
– Is the smallest unit of matter that still retains
the properties of an element
Subatomic Particles
• Atoms of each element
– Are composed of even smaller parts called
subatomic particles
• Relevant subatomic particles include
– Neutrons, which have no electrical charge
– Protons, which are positively charged
– Electrons, which are negatively charged
•
Protons and neutrons
are found in the atomic
nucleus
•
Electrons surround the
nucleus in a “cloud”
Cloud of negative
charge (2 electrons)
Electrons
Nucleus
(a) This model represents the
Figure 2.4
electrons as a cloud of
negative charge, as if we had
taken many snapshots of the 2
electrons over time, with each
dot representing an electron‘s
position at one point in time.
(b) In this even more simplified
model, the electrons are
shown as two small blue
spheres on a circle around the
nucleus.
Atomic Number and Atomic Mass
• Atoms of the various elements
– Differ in their number of subatomic particles
• The atomic number of an element
– Is the number of protons
– Is unique to each element
Example: Carbon has an atomic number of 6. If you know the atomic
number, you know the element. Usually, in naturally occurring elements, the
number of protons = the number of electrons. Therefore the atom has a
neutral charge. The properties of atoms are determined by the number and
arrangement of their electrons.
The mass number of an element
– Is the sum of protons plus neutrons in the
nucleus of an atom
– Is an approximation of the atomic mass of an
atom
– One mole of protons or neutrons has a mass
of one gram.
Isotopes – atoms of an element may occur in different forms
• Isotopes of a given element
– Differ in the number of neutrons in the atomic
nucleus
– Have the same number of protons
Radioactive isotopes
– Are unstable and spontaneously give off
particles and energy
– Radioactivity has negative effects, as when it
causes cancer, but also has positive uses, as
when it is used as a marker in biological
molecules.
Radioactive isotopes
– Can be used in biology
Cancerous
throat
tissue
Figure 2.6
Atomic structure of atoms determines how they interact.
Electron orbitals
• Electrons are located in specific energy levels
around the nucleus. You will need to know the
number of electrons in the outermost (reactive)
energy level for the different elements. The
total number of electrons = the total number of
protons (atomic number)
• DO NOT ASSUME A CHARGE on any atom
unless you see a charge symbol.
• Energy levels
– Are represented by electron shells
Third energy level (shell)
Second energy level (shell)
Energy
absorbed
First energy level (shell)
Energy
lost
Atomic
nucleus
Figure 2.7B
(b) An electron can move from one level to another only if the energy
it gains or loses is exactly equal to the difference in energy between
the two levels. Arrows indicate some of the step-wise changes in
potential energy that are possible.
• The periodic table of the elements
– Shows the electron distribution for all the
elements
Hydrogen
1H
Atomic mass
First
shell
2
He
4.00
Atomic number Helium
2He
Element symbol
Electron-shell
diagram
Lithium
3Li
Beryllium
4Be
Boron
3B
Carbon
6C
Nitrogen
7N
Oxygen Fluorine
8O
9F
Neon
10Ne
Second
shell
Sodium Magnesium Aluminum Silicon Phosphorus Sulfur
13Al
16S
11Na
12Mg
14Si
15P
Third
shell
Figure 2.8
Chlorine
17Cl
Argon
18Ar
• Valence electrons
– Are those in the outermost, or valence shell
– Determine the chemical behavior of an atom
Figure 4.4
• Each electron shell
– Consists of a specific number of orbitals
Electron orbitals.
Each orbital holds
up to two electrons.
x
Y
Z
1s orbital
2s orbital
Three 2p orbitals
1s, 2s, and 2p orbitals
Electron-shell diagrams.
Each shell is shown with
its maximum number of
electrons, grouped in pairs.
Figure 2.9
(a) First shell
(maximum
2 electrons)
(b) Second shell
(maximum
8 electrons)
(c) Neon, with two filled shells
(10 electrons)
Bonding Rules
• 1. Interactions are based on exchange or
rearrangement of electrons in the outer shell (valence
shell), also called valence electrons. (valence # is # of
e- needed to fill outer shell).
• 2. Stable atoms have a full outer shell.
• 3. Atoms that have 1, 2, or 3 valence e- tend to lose
them in reactions with atoms that have 5, 6, or 7, and
thus form + ions.
• 4. Atoms that have 5, 6, or 7 valence e- tend to gain
those lost by those with 1, 2, or 3, and thus form ions.
• 5. Atoms with 4 valence e- tend to share = covalent
bonds