Transcript Chaetodon ocellata

Chapter 5
Basics of Life: Molecules,
Cells, Evolution, and
Biological Classification
© 2006 Thomson-Brooks Cole
Key Concepts
• To understand living organisms, one
must have a basic understanding of
the variety of compounds from which
organisms are built.
• Four groups of macromolecules are
necessary for life: carbohydrates,
lipids, proteins, and nucleic acids.
• All living organisms are composed of
cells.
© 2006 Thomson-Brooks Cole
Key Concepts
• Cells can be either prokaryotic or eukaryotic.
• Cells produce new cells by the process of cell
division.
• Evolution is the process by which the genetic
composition of populations of organisms
changes over time.
• Natural selection favors the survival and
reproduction of those organisms that
possess variations that are best suited to
their environment.
© 2006 Thomson-Brooks Cole
Key Concepts
• A species is a group of physically
similar, potentially interbreeding
organisms that share a gene pool, are
reproductively isolated from other such
groups, and are able to produce viable
offspring.
• The binomial system of nomenclature
uses two words, the genus and the
species epithet, to identify an
organism.
© 2006 Thomson-Brooks Cole
Key Concepts
• Most biologists classify organisms into
one of three domains, categories that
reflect theories about evolutionary
relationships.
© 2006 Thomson-Brooks Cole
Building Blocks of Life
• Large molecules called macromolecules
are some of the most important
chemical compounds in organisms
• 4 major classes of macromolecules:
– carbohydrates
– lipids
– proteins
– nucleic acids
© 2006 Thomson-Brooks Cole
Carbohydrates
• Contain C, H and O, frequently in a
1:2:1 ratio – CH2O
• Sugars
– monosaccharides are simple sugars,
usually with 5 or 6 C atoms
• ribose and deoxyribes are in nucleic acids
• glucose is the basic fuel molecule for cells
– disaccharides consist of 2
monosaccharides bonded together
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Carbohydrates
– types of disaccharides
• sucrose = glucose + fructose (table sugar)
• maltose = glucose + glucose
• lactose = glucose + galactose (milk sugar)
• Polysaccharides
– these carbohydrates are polymers, large
molecules consisting of the same basic
units linked together
© 2006 Thomson-Brooks Cole
Carbohydrates
– storage forms of polysaccharides
• starches in plants, algae, and some
microorganisms, made of units of glucose
• glycogen, “animal starch” is similar
– structural polysaccharides
• cellulose is found in cell walls of plants, algae
• chitin is in fungi cell walls and exoskeletons of
some marine animals
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Lipids
• Composed primarily of C and H
– fatty acids—long hydrocarbon chains containing
an acid group
– triglycerides—simple fats composed of 3 fatty
acids attached to a glycerol molecule
• Functions within marine organisms
– store energy, cushion organs, buoyancy
– phospholipids are part of cell membranes
– steroids, which have complex ring structures, are
chemical messengers
– waxes act as a covering or water barrier
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Proteins
• Proteins are polymers of amino acids
– 20 amino acids make up proteins
– polypeptides—chains of amino acids,
which are coiled and folded into complex,
three-dimensional protein molecules
• Functions of proteins
– compose primary structural components
of animals: muscles and connective tissue
– enzymes—biological catalysts
– transport or store
chemicals
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Nucleic Acids
• Nucleic acids—polymers of nucleotides
– nucleotide = 5-carbon sugar + nitrogencontaining base + phosphate group
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Nucleic Acids
• DNA (deoxyribonucleic acid)
– large helix-shaped molecule
• sugar = deoxyribose
• N-containing base = adenine, guanine,
cytosine or thymine
– DNA contains genes (genetic material)
– genes direct synthesis of proteins
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Nucleic Acids
• RNA (ribonucleic acid)
– usually a single-stranded molecule
• sugar = ribose
• N-containing base = adenine, guanine,
cytosine or uracil
– functions in protein synthesis
• messenger RNA (mRNA)
• ribosomal RNA (rRNA)
• transfer RNA (tRNA)
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Cells
• Cells are basic units of living organisms
• All cells are capable of basic processes:
– metabolism
– growth
– reproduction
• Surrounded by cell membrane
• Cytoplasm contains cytosol (fluid
content of cell) and organelles
© 2006 Thomson-Brooks Cole
Types of Cells
• Prokaryotic cells (e.g. bacteria,
archaeans)
– lack a nucleus and membrane-bound
organelles
– prokaryotes (prokaryotic organisms) are
always unicellular
• Eukaryotic cells (e.g. plants, animals)
– have a well-defined nucleus and many
membrane-bound organelles
– eukaryotes may be uni- or multicellular
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Organelles
• Nucleus and ribosomes
– nucleus—large structure surrounded by a
nuclear membrane which contains the
cell’s DNA and acts as the control center
• chromosomes = DNA + protein
– ribosomes, which function in assembly of
proteins, are assembled in an area of the
nucleus called the nucleolus
© 2006 Thomson-Brooks Cole
Organelles
• Organelles involved in synthesis,
processing, and storage
– endoplasmic reticulum (ER)—series of
membranes winding through cytoplasm
• rough ER has ribosomes attached to its
surface, and functions in modification of
proteins during synthesis
• smooth ER (no ribosomes) functions in
synthesis of lipids and carbohydrates, and
detoxification of harmful substances
© 2006 Thomson-Brooks Cole
Organelles
– Golgi apparatus—organelle which
functions in the modification of proteins
and places plasma membranes around
them
– lysosomes—membrane-bound sacs
produced by the Golgi apparatus which
contain enzymes that function in digestion
– vacuoles—structures surrounded by a
plasma membrane that may contain food,
wastes, or water
© 2006 Thomson-Brooks Cole
Organelles
• Organelles involved in energy
conversion (reproduce themselves)
– chloroplasts—organelles found in
photosynthetic organisms that function in
converting radiant energy of light into
chemical energy
– mitochondria—organelles which transfer
chemical energy in food to molecules of
adenosine triphosphate (ATP)
• ATP supplies energy for metabolism
© 2006 Thomson-Brooks Cole
Organelles
• Organelles of movement
– flagella—long, hair-like organelles (usually
1, 2 or 3 per cell) used to propel the cell
through the watery environment
– cilia—short, hair-like organelles which are
quite numerous, sometimes covering the
cell surface; used by single cells to move
through the water, and to move materials
along the cell’s surface in multicellular
organisms
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Energy Transfer in Cells
© 2006 Thomson-Brooks Cole
Energy Transfer in Cells
• Photosynthesis
– low-energy molecules (CO2 and H2O)
combine to form high-energy food
molecules (carbohydrates)
– in prokarytes, occurs in areas of thecell
where the membrane has folded in to
form a surface for needed participants
– chloroplasts
• two membranes
• thylakoids, arranged in stacks (grana)
• stroma—fluid containing enzymes necessary
for carbon fixation
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Energy Transfer in Cells
• Cellular respiration
– releases energy from food molecules
– most occurs within mitochondria
• two membranes, with inner membrane folded
many times to form mitochondrial cristae
– food molecules are broken down to create
some ATP and release CO2 as a waste
product
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Cellular Reproduction
• Cell division in prokaryotes
– have a single, circular chromosome
– binary fission—chromosome is duplicated,
and cell splits into 2 daughter cells
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Cellular Reproduction
• Cell division in eukaryotes
– mitosis—(occurs after duplication of all
chromosomes) nuclear membrane
disappears, chromosomes separate, and
new membranes form to make 2 copies
– after mitosis, the cell divides (cytokinesis)
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Levels of Organization
• Cells within a multicellular organism
that serve 1 particular function are
grouped into tissues
• Tissues combine into structures called
organs
• Groups of organs make up organ
systems
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Evolution and Natural
Selection
• Evolution—the process by which
populations of organisms change over
time
• Evolutionary biology investigates:
– how and when organisms evolved
– what role the environment plays in
determining the characteristics of
organisms that can live in a given area
© 2006 Thomson-Brooks Cole
Darwin and the Theory for
Evolution
• Voyage of discovery
– Darwin traveled on the HMS Beagle for 5
years, beginning in 1831
– Darwin read books by geologist Charles
Lyell, and was influenced by his
conclusions:
• since geological change is slow and
continuous, the earth is very old
• slow and subtle changes become substantial
when they continue for centuries/millenia
© 2006 Thomson-Brooks Cole
Darwin and the Theory for
Evolution
• Formulating a theory for evolution
– Darwin was inspired by Thomas Malthus’s
essay about factors that control the
human population
– Darwin developed his hypothesis
“evolution by natural selection” to explain
why populations generally do not exhibit
unchecked growth and how they change
over time
– published in On the Origin of Species by
Means of Natural Selection
© 2006 Thomson-Brooks Cole
Darwin and the Theory for
Evolution
• Theory of evolution by natural
selection
– artificial selection is practiced by farmers
to obtain desirable traits in plants/animals
– natural selection favors survival and
reproduction of those organisms best
suited to their environment
• selective forces—physical and biological
characteristics of the environment that favor
survival of one species over another
• e.g. temperature, salinity, predation, etc.
© 2006 Thomson-Brooks Cole
Darwin and the Theory for
Evolution
– 4 basic premises of Darwin’s theory
1. All organisms produce more offspring than
can possibly survive to reproduce.
2. There is a great deal of variation in traits
among individuals in natural populations.
Many of these variations can be inherited.
3. The amount of resources necessary for
survival is limited. Therefore organisms must
compete with each other for these resources.
© 2006 Thomson-Brooks Cole
Darwin and the Theory for
Evolution
1. Those organisms that inherit traits that make
them better adapted to their environment are
more successful in the competition for
resources. They are more likely to survive
and produce more offspring. The offspring
inherit their parents’ traits, and they continue
to reproduce, increasing the number of
individuals in a population with the
adaptations necessary for survival.
– an organism evolves traits that are
beneficial, as well as traits that are
neither harmful nor beneficial
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Genes and Natural Selection
• Modern evolutionary theory
– the modern synthetic theory of evolution
is essentially Darwin’s 1858 idea refined
by modern genetics
– genes
• produce traits when genetic information is
translated into proteins by protein synthesis
• can exist in different forms called alleles
• the offspring receives 1 allele for a trait from
each parent, producing many possible
combinations of alleles in the offspring
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Genes and Natural Selection
• Role of reproduction
– in asexual reproduction, offspring are
clones of the single parent, and variation
may only result from mutation
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Genes and Natural Selection
• Role of reproduction
– chromosomes from 2 parents are
combined in sexual reproduction
• gametes (sex cells) unite during fertilization
• gametes have a haploid number (N) of
chromosomes instead of a diploid number (2N)
• the haploid number of chromosomes from 2
gametes combine to form the diploid number
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Genes and Natural Selection
– meiosis (reduction division) is the process
through which gametes are formed
• chromosomes are duplicated once, and the cell
divides twice
• results in cells with ½ the number of
chromosomes in the parent cell
• during the initial phase, chromosomes connect
and allow crossing over and recombination
• meiosis increases variety by shuffling the gene
pool
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Genes and Natural Selection
• Population genetics
– organisms must adapt to changing
environmental conditions to survive
– ability to adapt is limited by the gene pool
– fitness (biological success) is measured by
the number of an organism’s own genes
that are present in the next generation
© 2006 Thomson-Brooks Cole
New Species Evolve from
Existing Species
• Typological definition of species
– typological definitions are based on
morphology, the structure and appearance
of the organism
– a species as defined this way will have a
definable set of characteristics different
from those of other species
– weaknesses of typological definition
• males may look different than females (sexual
dimorphism) and juveniles than adults
• there may be great variations in appearance
within a single population (e.g. color)
© 2006 Thomson-Brooks Cole
New Species Evolve from
Existing Species
• Modern species definition
– a species is one or more populations of
potentially interbreeding organisms that
are reproductively isolated from other
such groups
– reproductive isolation—members of a
different species are not in the same place
at the same time or are physically
incapable of breeding, so genes from
different species are not mixed
© 2006 Thomson-Brooks Cole
New Species Evolve from
Existing Species
– isolating mechanisms that prevent
fertilization
• habitat isolation—similar species of organisms
live apart and never encounter each other
• anatomical isolation—incompatible copulatory
organs prevent similar species from
reproducing with one another
• behavioral isolation—exhibiting of special
behaviors during the breeding season, so that
only members of the same species recognize
the behavior as courtship
© 2006 Thomson-Brooks Cole
New Species Evolve from
Existing Species
• temporal isolation—the time members of one
species are ready to reproduce does not
coincide with the time members of a related
species reproduce
• biochemical isolation—biochemical or genetic
differences between the gametes of 2 species
prevent successful copulation from resulting in
offspring
© 2006 Thomson-Brooks Cole
New Species Evolve from
Existing Species
– isolating mechanisms that prevent
successful reproduction following
fertilization
• incompatible genes or biochemical differences
can prevent a fertilized egg from developing
• the hybrid offspring may survive but be
infertile or poorly equipped to compete (so
that it dies without reproducing)
© 2006 Thomson-Brooks Cole
New Species Evolve from
Existing Species
• Process of speciation
– allopatric speciation—2 or more
populations of the same species become
geographically isolated
– gene flow between the 2 populations stops
– natural selection operates of each
segment of the original population
independently
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Linnaeus and Biological
Classification
• Binomial system of naming
– binomial nomenclature—system of naming
that uses 2 words, the genus and species
epithet
– introduced by Swedish botanist Karl von
Linné (Carolus Linnaeus) in 1750
– e.g. Chaetodon longirostris (long-nose
butterflyfish) and Chaetodon ocellata
(spotfin butterflyfish) are both in the same
genus
© 2006 Thomson-Brooks Cole
Linnaeus and Biological
Classification
• Taxonomic categories
– Early schemes of classification
• all living things were classified into 1 of 2
kingdoms, Animalia and Plantae, until 1960s
– Modern classification
• major categories: domain, kingdom, phylum,
class, order, family, genus, and species
• domains: Archaea, Eubacteria, Eukarya
• kingdoms: Eukarya contains 3 kingdoms,
Fungi, Plantae and Animalia
• protists—eukaryotic organisms that do not fit
the definition of animal, plant or fungus
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Archaebacteria live in extreme conditions
© 2006 Thomson-Brooks Cole
Sand-dwelling marine fungus (Corollospora)
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole