Download Chapter 5 Key Concepts • To understand living organisms, one must

Chapter 5
Key Concepts
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To understand living organisms, one must have a basic understanding of the variety
of compounds from which organisms are built.
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Four groups of macromolecules are necessary for life: carbohydrates, lipids,
proteins, and nucleic acids.
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All living organisms are composed of cells.
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Cells can be either prokaryotic or eukaryotic
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Cells produce new cells by the process of cell division
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Evolution is the process by which the genetic composition of populations of
organisms changes over time
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Natural selection favors the survival and reproduction of those organisms that
possess variations that are best suited to their environment
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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.
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The binomial system of nomenclature uses two words, the genus and the species
epithet, to identify an organism.
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Most biologists classify organisms into one of three domains, categories that reflect
theories about evolutionary relationships.
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Phylogenetic trees and cladograms indicate evolutionary relationships among
groups of organisms
Building Blocks of Life
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Macromolecules
– carbohydrates
– lipids
– proteins
– nucleic acids
Carbohydrates
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Contain C, H and O
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Sugars and polysaccharides most common carbohydrates
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Sugars
– monosaccharides
• ribose and deoxyribose are in nucleic acids
• glucose is the basic fuel molecule for cells
– disaccharides
• sucrose
• maltose
• lactose
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Polysaccharides
– polymers
– storage forms
• starches, made of glucose
• glycogen, “animal starch”
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structural polysaccharides
• cellulose
• chitin
Lipids
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Fats, Oils & Waxes
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Composed of C and H
– fatty acids
– Triglycerides
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Functions within marine organisms
– store energy, cushion organs, buoyancy
– cell membranes
– steroids
– waxes
Proteins
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Proteins are polymers of amino acids
– 20 amino acids
– polypeptides
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Functions of proteins
– muscles and connective tissue
– enzymes—biological catalysts
– transport or store chemicals
Nucleic Acids
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DNA (deoxyribonucleic acid)
– Large, double stranded, helix-shaped molecule
• N-containing base = adenine, guanine, cytosine or thymine
• contains genes (genetic material)
• genes direct synthesis of proteins
• can copy itself so that genes can be past from one generation to the
next
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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
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All cells are capable of:
– metabolism
– growth
– Reproduction
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Cell membrane
Cytoplasm, within the cell membrane is composed of cytosol and organelles
Organelles
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Nucleus and ribosomes
– Nucleus: contains the cell’s DNA and acts as the control center
– Ribosomes
– endoplasmic reticulum
• rough ER
• smooth ER
– Golgi apparatus
– lysosomes
– Vacuoles
– chloroplasts
– mitochondria
– Flagella
– Cilia
Energy Transfer in Cells
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Photosynthesis
– low-energy molecules combine to form high-energy food molecules
– chloroplasts
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Cellular respiration
– releases energy from food molecules
– most occurs within mitochondria
– food molecules are broken down to create ATP and release CO2 as a waste
product
Cellular Reproduction
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Cell division in prokaryotes
– single chromosome
– binary fission
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Cell division in eukaryotes
– Mitosis
– Cytokinesis
Levels of Organization
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cells are grouped into tissues
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different tissues combine into organs
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groups of organs make up organ systems
Evolution and Natural Selection
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Evolution—the process by which populations of organisms change over time
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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
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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
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Formulating a theory for evolution
– Darwin was inspired by Thomas Malthus
– Darwin developed his hypothesis “evolution by natural selection”
– Published On the Origin of Species by Means of Natural Selection
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Theory of evolution by natural selection
– artificial selection
– similar process was occurring in nature?
– natural selection favors survival and reproduction of those organisms best
suited to their environment
Four basic premises of Darwin’s theory
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All organisms produce more offspring than can possibly survive to
reproduce.
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Variation in inherited traits
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Resources are limited
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Traits that make individuals better adapted to their environment are
more successful, and pass on those traits to their offspring.
Genes and Natural Selection
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Modern evolutionary theory
– Darwin’s 1858 idea refined by modern genetics
– genes
• produce traits
• can exist in alleles
• the offspring receives 1 allele for a trait from each parent, producing
many possible combinations
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Role of reproduction
– in asexual reproduction, offspring are clones
– variation results from mutation only
– in sexual reproduction, chromosomes from 2 parents are combined
– meiosis forms haploid cells called gametes
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Population genetics
– Organisms adapt 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
– Reproduction is success
Evolution of New Species
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Typological definition of species
– based on morphology
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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
– isolating mechanisms that prevent fertilization
• habitat isolation
• anatomical isolation
• behavioral isolation
• temporal isolation
• biochemical isolation
Post fertilization isolating mechanisms
• incompatible genes or biochemical differences
• the hybrid offspring may survive but be infertile or weak
Allopatric speciation
Classification: Bringing Order to Diversity
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Linnaeus and the binomial system
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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
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Phylogeny:
– phylogenetic tree
– phenetics
– cladistics