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Chapter 5
Biological Concepts
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Key Concepts
• Cells can be either prokaryotic or eukaryotic
• Prokaryotic – no membrane bound organelles
» Bacteria
• Eukaryotic – membrane bound organelles, more complex
» Protists, fungi, plants, animals
• 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
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.
• Homo sapiens or Homo sapiens - human
• Callinectus sapidus or Callinectus sapidus – blue
crab
• Common names can be confusing, the scientific
name allows you to know the organism no matter
what language you speak
• Now, most biologists classify organisms
into one of three domains, categories that
reflect theories about evolutionary
relationships.
• Phylogenetic trees and cladograms
indicate evolutionary relationships among
groups of organisms
• 3 Domains of Life:
• Archaea – prokaryotic
» Includes extremophile bacteria
• Bacteria – prokaryotic
» Includes bacteria formerly in Kingdom Monera
• Eukarya – eukaryotic cells
» Inlcudes protists, fungi, plants and animals
– The numbers in Archaea and Bacteria far outnumber the
numbers in Eukarya
Building Blocks of Life
• Macromolecules (large molecules) are
some of the most important chemical
compounds in organisms
• 4 major classes of macromolecules in
living organisms are:
– carbohydrates
– lipids
– proteins
– nucleic acids
Carbohydrates
• Contain C, H and O, frequently in a 1:2:1
ratio
• CH2O - thus the name carbohydrate (carbon
water)
Carbohydrates
• 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
• types of disaccharides:
– sucrose = glucose + fructose (table sugar)
– maltose = glucose + glucose
– lactose = glucose + galactose (milk sugar)
Carbohydrates
• Polysaccharides
– these carbohydrates are polymers, large molecules consisting of
the same basic units linked together
– storage forms of polysaccharides
• starches – found in plants, algae, and some microorganisms,
made of units of glucose
• glycogen, “animal starch” - is produced by animals and some
microorganisms to store glucose for future use
– structural polysaccharides
• cellulose is found in cell walls of plants, algae
• chitin is in fungi cell walls and exoskeletons of some marine
animals
Lipids
• Fats, Oils & Waxes
• 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, e.g., testosterone
– waxes act as a covering or water barrier
Proteins
• Proteins are polymers of amino acids
– 20 different amino acids make up proteins
– polypeptides—chains of amino acids, which
are coiled and folded into complex, threedimensional protein molecules
• Functions of proteins
– compose primary structural components of
animals: muscles and connective tissue
– enzymes—biological catalysts
– transport or store chemicals
Nucleic Acids
• Nucleic acids—polymers of nucleotides
– Nucleotides are composed of 5-carbon sugar
+ nitrogen-containing base + phosphate group
• DNA & RNA
- two types of nucleic acids found in living
organisms
Nucleic Acids
• DNA (deoxyribonucleic acid)
– Large, double stranded, helix-shaped molecule
• sugar = deoxyribose
• N-containing bases
–
–
–
–
A: adenine
G: guanine
C: cytosine
T: thymine
– DNA
• A section of DNA is called a gene (genetic material)
• genes code for proteins
• can copy itself so that genes can be past from one
generation to the next
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)
Cells
• Cells are basic units of living organisms
• All cells are capable of basic processes:
– metabolism
– growth
– reproduction
• Surrounded by cell membrane
• Cytoplasm, within the cell membrane is
composed of cytosol (fluid content of cell)
and organelles
Types of Cells
• Prokaryotic cells (bacteria, archaeans)
– lack a nucleus and membrane-bound
organelles
– prokaryotes (prokaryotic organisms) are
always unicellular
• Eukaryotic cells (protists, fungi, plants,
animals)
– have a well-defined nucleus and many
membrane-bound organelles
– eukaryotes may be uni- or multi-cellular
Organelles
•
•
•
•
•
•
•
Have specific functions within cell
Nucleus
Mitochondria
Chloroplasts
Endoplasmic reticulum
Lysosomes
vacuoles
Energy Transfer in Cells
Energy Transfer in Cells
• Photosynthesis
– low-energy molecules (CO2 and H2O) combine
to form high-energy food molecules
(carbohydrates)
– Primary producers perform photosynthesis
• Cyanobacteria
• Some eukaryotes do photosynthesis – algae and
plants
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
ATP and release CO2 as a waste product
Cellular Reproduction
• Cell division in prokaryotes
– Bacteria only have 1 single, circular
chromosome
• binary fission—chromosome is duplicated, and cell
splits into 2 daughter cells
Cellular Reproduction
• Cell division in eukaryotes
– Eukaryotes have multiple linear chromosomes
– # depends on species
– Have to use mitosis to ensure a copy of each
chromosome ends up in each new cell
– Process:
• Chromosomes duplicate
• Mitosis
–
–
–
–
Prophase
Metaphase
Anaphase
Telophase
• Cytokenesis – the division of the cell
Levels of Organization
• All living things are made up of at least one cell
• Prokaryotes (bacteria) are made of one cell
• Eukaryotes can be unicellular (some protists) or
multicellular (protists, fungi, plants, animals)
– Multicellular level of organization:
– Cell
– Group of specialized cells makes up a tissue
– Couple of tissues makes an organ
– Organs make up organ systems
– Organ systems make up an individual
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
Darwin and the Theory for Evolution
• Voyage of discovery
– Darwin traveled on the HMS Beagle for 5
years, beginning in 1831
– Darwin was influenced by Charles Lyell and
other geologists who concluded that:
• since geological change is slow and continuous,
the earth is very old
• slow and subtle changes become substantial when
they continue for centuries/millennia
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
Darwin and the Theory for Evolution
• Theory of evolution by natural selection
– artificial selection is practiced by farmers and
breeders to obtain desirable traits in
plants/animals
– We pick our domesticated animals and crops based on
desirable traits
– All of our domesticated species look very different from
their ancestors
– Darwin believed a similar process was
occurring in nature
– natural selection favors survival and
reproduction of those organisms best suited
to their environment
Darwin and the Theory for Evolution
–
Four 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 (e.g., food, light, living space)
necessary for survival is limited. Therefore organisms must
compete with each other for these resources.
4. 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.
Darwin and the Theory for Evolution
– New traits arise due to mutations in the DNA
– Mutations are random and it might take
many over a long period of time to lead to a
new trait
– an organism evolves traits that are
beneficial, as well as traits that are neither
harmful nor beneficial
• Natural selection
• There will be some individuals in the population
that have traits that make them suited for the
environment or a change in the environment
» Those individuals will be more successful at finding
food and surviving. This will make them more likely
to successfully have offspring, therefore passing on
those traits.
• Evolution does not necessarily lead to
perfection
• Environmental pressures cause advantageous
traits to persist
• Those traits have to be present to be subjected to
the environmental pressure
» An organism cannot “wish” to have a desirable trait.
Random mutation of DNA leads to new traits that just
might be beneficial in the current environment
» Also leads to traits that are not beneficial or harmful,
they are just traits that are there
Genes and Natural Selection
• When Darwin proposed theory of evolution
by natural selection, cell division, genes and
chromosomes had not been discovered.
• 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
• 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
Genes and Natural Selection
• Role of reproduction
– in asexual
reproduction, offspring
are clones of and
identical the single
parent, variation
results from mutation
only
Genes and Natural Selection
• Role of reproduction
– in sexual reproduction, chromosomes from 2
parents are combined
• 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
Genes and Natural Selection
• Role of reproduction (con’t)
– meiosis (reduction division) is special kind of
cell division that forms haploid cells called
gametes
Genes and Natural Selection
• Population genetics
– organisms must adapt to changing
environmental conditions in order to survive
– ability to adapt is limited by the gene pool
– Only individuals that have combinations of
genes and alleles that allow adaptations to their
surroundings are likely to survive and
reproduce
– fitness (biological success) is measured by the
number of an organism’s own genes that are
present in the next generation
Evolution of New Species
•
•
Modern species definition
– a species is one or more populations of potentially interbreeding organisms that
are reproductively isolated from other such groups
Isolation leading to speciation can happen many different ways:
– 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
– 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
– 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
Classification: Bringing Order to Diversity
• Phylogeny: evolutionary history of a
species or group of related species
– phylogenetic tree: traditional representation of
phylogeny
– phenetics: classification of organisms based
on similar characteristics with little attention to
when these characteristics evolved.
– cladistics: bases classification on the order in
time that the branches arise along a
phylogenetic tree called a cladogram, ignores
similarity of structure