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Chapter 5 Biological Concepts Karleskint Turner Small 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