Chapter 2
1.8
What Is Ecology? (p.
32; Fig. 2.18)
A.
Ecology is the study of how organisms that live in a place
interact with each other and their physical
habitat.
Levels of Ecological Organization
1.
Populations are members of
the same species that live together and potentially breed with one another.
2.
Communities are made up of
populations of different species that utilize different resources within the
habitat that they share.
3.
Ecosystems are the
communities interacting with their nonliving habitats; ecosystems regulate the
flow of energy and cycling of nutrients.
4.
Population ecologists study
the dynamics of a species; community ecologists study how species interact with
each other; systems ecologists are interested in how biological communities interact
with their physical habitats.
1.9
Ecosystems (p. 33;
Fig. 2.19)
A.
Ecosystems are the
fundamental units of ecology.
B.
Energy Flows Through
Ecosystems
1.
All of the energy that passes
through a community comes ultimately from the sun.
2.
Energy flows through the ecosystem
from plant to herbivore to carnivore.
C.
Materials Cycle Within
Ecosystems
1.
As organisms decompose after
death, the materials of their bodies pass back into the ecosystem.
2.
Materials cycle between
organisms and their physical environment.
D.
Major Ecosystems
1. The two most important factors determining the nature of an ecosystem in an area are rainfall and temperature.
3 The Chemistry of Life
EXTENDED LECTURE OUTLINE
3.1 Atoms (p. 44; Figs. 3.1, 3.2)
A. All matter is composed of atoms and atoms are the smallest particles into which a substance can be divided and still retain its chemical properties.
B. An atom has positively charged protons and neutrally charged neutrons in the nucleus, with tiny negatively charged electrons whizzing about the nucleus.
C. Ions
1. In an electrically neutral atom, there are equal numbers of protons and electrons.
2. Ions form when atoms do not have equal numbers of electrons and protons.
3.2 Electrons Determine What Atoms Are Like (p. 45; Figs. 3.3, 3.4)
A. Electrons determine how an atom will interact with other
atoms.
B. Electrons Carry Energy.
1.
Electrons possess energy, and
energy levels surrounding the nucleus reflect the amount of energy possessed by
an electron existing there.
2.
Less energy is present in
electrons closer to the nucleus.
3.
Electrons are most likely to
be found in volumes of space called orbitals.
4.
There are different shell
level: the first shell has one orbit and can hold two electrons.
5.
The second and third energy
shell level each have four orbitals, and can hold up to eight electrons apiece.
6. When orbitals are not filled with electrons, the atoms are likely to react with atoms to fill orbitals.
3.3 Molecules (p. 48; Figs. 3.8, 3.9, 3.10)
A. A molecule is made up of two or more atoms held together by a chemical bond.
B. Chemical bonds form between atoms as a result of interactions between electrons.
C. Ionic Bonds
1. Ionic bonds form when ions are electrically attracted to each other by opposite charges.
2. Table salt is built of ionic bonds.
3. Sodium gives up an electron to chloride; sodium then bears a positive charge while chloride bears a negative charge; these two ions combine to form table salt (NaCl).
4. Ionic bonds are strong and not directional, two properties that help them form crystals.
D. Covalent Bonds
1. Covalent bonds form when electrons are shared between atoms.
2. Most organic molecules are formed from covalent bonds.
3. Two key properties make covalent bonds ideal for use in biological molecules: they are strong and they are very directional.
E. Hydrogen Bonds
1. Hydrogen bonds are the result of weak electrical attractions between hydrogen atoms and the larger atoms of polar molecules.
2.
Hydrogen bonds are weak and
highly directional, and thus play an important role in maintaining the
conformation of large, biologically important molecules.
A. High Polarity
1.
Other polar, hydrophilic,
molecules are “welcomed” by water molecules, which form shells of water
molecules around each of the other polar molecules such that these molecules
are soluble in water.
2. Non-polar molecules, by contrast, are hydrophobic and are not soluble in water.
3.4 Forming Macromolecules (p. 54; Figs. 3.17, 3.18; Table 3.3)
A. Four major categories of organic molecules are found in living things.
B. Large organic molecules are called macromolecules because of their size and complexity.
C. A macromolecule is a polymer built from repeating subunits.
D. Organic molecules are based on long chains of carbon with functional groups on the ends that give the molecules their unique chemical properties.
3.5 Carbohydrates (p. 56; Figs. 3.19, 3.20, 3.21)
A. Carbohydrates are used as energy sources and are made up of polymers of simple carbohydrates.
B. Simple Carbohydrates
1.
The simple sugars, or
monosaccharides, consist of one subunit.
2. Another simple carbohydrate is a disaccharide, built of two subunits.
C. Complex Carbohydrates
1. Animals and plants store energy in polysaccharides formed from glucose.
2. Examples of complex carbohydrates include glycogen, chitin, cellulose, and starch.
3.6 Lipids (p. 57; Figs. 3.22, 3.23)
A. Fats and all other biological molecules that are not soluble in water but are soluble in oil are lipids.
B. Fats are employed for long-term storage of energy.
C. Fats
1. Triacylglycerol molecules (triglycerides) are made up of glycerol and three fatty acids.
2. The fatty acids may be saturated or unsaturated with hydrogen along the carbon chain.
D. Other Types of Lipids
1. Phospholipids are used to build biological membranes.
2. A third type of lipid, steroids, serve a number of functions within the cell.
3.7 Proteins (p. 58; Figs. 3.24, 3.25, 3.26)
A. Proteins can serve as enzymes, play structural roles, and act as chemical messengers.
B. Proteins are polypetides made up of amino acids joined together by peptide bonds.
C. Protein Structure
1. The sequence of amino acids within a protein is called the primary structure.
2. The secondary structure is any folding of the primary chain.
3. Globular shapes are the tertiary structure of a protein.
4. When more than one polypeptide chain composes the protein, it is said to have quaternary structure.
5. The shape of a protein can be denatured, which prevents it from functioning properly.
6. Many proteins serve as enzymes, which function as catalysts in chemical reactions.
12 How We Name Living Things
12.1The Invention of the Linnaean System (p. 278; Fig. 12.1)
A. Any system that attempts to group and categorize organisms is called a classification scheme.
B. Prior to using the current system, which employs two-part names, or binomials, a variety of other systems were in use from the time of Greek philosopher Aristotle on.
C. The basic unit, called a genus (plural, genera), has been used since the time of the Greeks and Romans.
D. A particular type of organism became known as a species.
E. The Polynomial System
1. Until the mid-1700s, strings of long polynomials, up to 12 words long, were used to classify organisms.
F. The Binomial System
1. The classification scheme in universal use today, a binomial system, was devised 200 years ago by Swedish biologist Carolus Linnaeus.
2. Two-part Latin names are used to name particular organisms.
12.2 Species Names (p. 279; Fig. 12.2)
A. By convention, the first part of a binomial name identifies the genus to which the species belongs, and the second part distinguishes one species from others in the genus.
B. The two names together are called the scientific name and are written in italics.
12.3 Higher Categories (p. 280; Fig. 12.3)
A.
The Linnaean system is a
hierarchical system that uses groupings, with each one in succession smaller
and more specific than the one before it.
B.
From largest to smallest, biologists
use the groupings kingdom, phylum, class, order, family, genus, and species.
C.
Each category is associated with a
specific type of characteristic, so each gives information about the organisms
grouped within it.
D. In addition, an eighth level of classification, called domains, is used.
12.4 What Is a Species? (p. 281; Fig. 12.4)
A. John Ray (1627-1705) was one of the first to propose a general definition of a species: all the individuals that belong to it can breed with one another and produce fertile offspring.
B. The Biological Species Concept
1. Evolutionist Ernst Mayr contributed to the biological
species concept with the statement that species are “groups of actually or potentially interbreeding natural populations
which are reproductively isolated from other such groups.”
2. It follows that hybrids occur rarely in nature, while members of the same species can readily interbreed.
C. Problems with the Biological Species Concept
1. The biological species concept definition works well for animals, but many of the organisms of the other kingdoms only rarely have sexual reproduction and outcrossing, but instead often reproduce by asexual reproduction.
2. The biological species concept is not always employed for plants and other organisms.
D. How Many Kinds of Species Are There?
1. About 1.5 million species have been named, and scientists estimate there may be as many as 10 million species on earth.
12.5 The Kingdoms of Life (p. 284; Fig. 12.7)
A. The earliest classification schemes recognized only animals and plants, but most scientists now use a six-kingdom system.
B. In the six-kingdom system, four kingdoms consist of eukaryotes and two of prokaryotes.
1. The kingdoms Animalia and Plantae contain organisms that are multicellular throughout most of their lifespans.
2. The kingdom Fungi contains multicellular forms and single-celled yeasts.
3. Animals, plants, and fungi all have fundamental differences and probably each descended from a different ancestor.
4. The kingdom Protista encompasses the algae and a large number of unicellular eukaryotes.
5. The remaining two kingdoms, Archaebacteria and Eubacteria, consist of prokaryotes that are vastly different from other living things.
C.
1. Archaebacteria, eubacteria, and eukaryotes are each in a separate domain.
D. Identification of organisms – Dichotomous Keys
1. Each step in the key has two choices
2. The descriptive choices group the organisms in to small units and ultimately identify each organism. Each dichotomous set either identifies an organism or directs the reader to the next dichotomous choice.
12.6 Archaebacteria (p. 285;
Fig. 12.8; Table 12.1)
A. The term archaebacteria refers to the ancient origins of this group which exist today in extreme environments.
B. Methanogens obtain their energy by using hydrogen gas to reduce carbon dioxide to methane gas.
1. These archaebacteria evolved before oxygen was present in the atmosphere and today live in swamps, marshes, and in mammalian intestines.
2. Methanogens contribute 2 billion tons of methane gas into the atmosphere annually.
C. Extremophiles include thermophiles (heat lovers), halophiles (salt lovers), and pressure-tolerant archaebacteria.
D. Nonextreme archaebacteria grow in habitats similar to eubacteria and are identified by their signature sequences.
12.7 Eubacteria (p. 286; Fig.
12.9; Table 12.2)
A. The eubacteria are the most abundant organisms on earth and are as different from the archaebacteria as they are from the eukaryotes.
B. There are many different kinds of eubacteria and the evolutionary links between them are not readily understood.
C. Archaebacteria appear to be more closely related to eukaryotes than they are to eubacteria.
Both the Archaebacteria and Eubacteria are referred to collective as prokaryotic organisms.
12.8 Domain Eukarya (Eukaryotes) (p. 287)
A. The eukaryotes appeared in the fossil record 1.5 billion years ago, much later than the prokaryotes.
B. Three Largely Multicellular Kingdoms
1. Because of the size and ecological importance of plants, animals, and fungi, and because they are mostly multicellular, they are recognized as kingdoms distinct from Prostista.
C. A Fourth Very Diverse Kingdom
1. Protists are a fascinating and diverse group of unicellular eukaryotes that have great biological significance.
D. Symbiosis and the Origin of Eukaryotes
1. Mitochondria and chloroplasts are both believed to have entered the early eukaryotic cells by endosymbiosis.
2. Each of these organelles is the size of a bacterium and bears its own DNA.
12.9 Viruses: A Special Case (p. 288; Figs.
12.10, 12.11)
A. Viruses appear to be fragments of nucleic acids originally derived from the genome of a living cell.
Viruses can infect organisms at all taxonomic levels, yet are not considered living because they do not satisfy the basic criteria for life.