2006 Thomson-Brooks Cole 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 CH 2 O 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 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 Lipids Composed primarily of C and H fatty acidslong hydrocarbon chains containing an acid group triglyceridessimple 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 Proteins Proteins are polymers of amino acids 20 amino acids make up proteins polypeptideschains 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 enzymesbiological catalysts transport or store chemicals 2006 Thomson-Brooks Cole Nucleic Acids Nucleic acidspolymers of nucleotides nucleotide = 5-carbon sugar + nitrogen- containing base + phosphate group 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 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 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 Organelles Nucleus and ribosomes nucleuslarge structure surrounded by a nuclear membrane which contains the cells 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 apparatusorganelle which functions in the modification of proteins and places plasma membranes around them lysosomesmembrane-bound sacs produced by the Golgi apparatus which contain enzymes that function in digestion vacuolesstructures surrounded by a plasma membrane that may contain food, wastes, or water 2006 Thomson-Brooks Cole Organelles Organelles involved in energy conversion (reproduce themselves) chloroplastsorganelles found in photosynthetic organisms that function in converting radiant energy of light into chemical energy mitochondriaorganelles 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 flagellalong, hair-like organelles (usually 1, 2 or 3 per cell) used to propel the cell through the watery environment ciliashort, 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 cells surface in multicellular organisms 2006 Thomson-Brooks Cole Energy Transfer in Cells 2006 Thomson-Brooks Cole Energy Transfer in Cells Photosynthesis low-energy molecules (CO 2 and H 2 O) 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) stromafluid containing enzymes necessary for carbon fixation 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 CO 2 as a waste product 2006 Thomson-Brooks Cole Cellular Reproduction Cell division in prokaryotes have a single, circular chromosome binary fissionchromosome is duplicated, and cell splits into 2 daughter cells 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 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 Evolution and Natural Selection Evolutionthe 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 Malthuss 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 forcesphysical 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 Darwins 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 Genes and Natural Selection Modern evolutionary theory the modern synthetic theory of evolution is essentially Darwins 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 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 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 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 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 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 organisms 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 isolationmembers 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 isolationsimilar species of organisms live apart and never encounter each other anatomical isolationincompatible copulatory organs prevent similar species from reproducing with one another behavioral isolationexhibiting 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 isolationthe time members of one species are ready to reproduce does not coincide with the time members of a related species reproduce biochemical isolationbiochemical 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 speciation2 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 Linnaeus and Biological Classification Binomial system of naming binomial nomenclaturesystem of naming that uses 2 words, the genus and species epithet introduced by Swedish botanist Karl von Linn (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 protistseukaryotic organisms that do not fit the definition of animal, plant or fungus 2006 Thomson-Brooks Cole Archaebacteria live in extreme conditions 2006 Thomson-Brooks Cole Sand-dwelling marine fungus (Corollospora) 2006 Thomson-Brooks Cole