Who, What, When, Where, Why, and How of Biological Concepts Who was Charles Darwin? What are the types of cells? What are the classes of macromolecules? When did eukaryotes evolve (before or after prokaryotes)? Where can chloroplasts be found? Why does meiosis lead to genetic variation? How do bacterial cells divide? Karleskint Small Turner Chapter 5 Biological Concepts 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 (at least one cell). 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 Callinectus sapidus or Callinectus sapidus Common names can be confusing, the scientific name allows you to know the organism no matter what language you speak Key Concepts 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 CH 2 O - thus the name carbohydrate (carbon water) Sugars and polysaccharides are the two most common carbohydrates in living organisms 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 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 Nucleic Acids Nucleic acidspolymers 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 base = adenine, guanine, cytosine or 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 (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 multi-cellular Organelles Have specific functions within cell Nucleus and ribosomes Nucleus: large structure surrounded by a nuclear membrane which contains the cells DNA and acts as the control center Chromosomes, which contain an organisms genes, is composed of DNA + protein ribosomes, which function in the synthesis of proteins, are assembled in an area of the nucleus called the nucleolus Energy Transfer in Cells Photosynthesis low-energy molecules (CO 2 and H 2 O) combine to form high-energy food molecules (carbohydrates) in eukaryotes, photosynthesis occurs within chloroplasts 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 CO 2 as a waste product Cellular Reproduction Cell division in prokaryotes Bacteria have a single, circular chromosome binary fissionchromosome is duplicated, and cell splits into 2 daughter cells 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) Cytokinesis = division of cell into two daughter cells Levels of Organization Cells within a multicellular organism that serve 1 particular function are grouped into tissues Several different tissues can combine into structures called organs Groups of organs make up organ systems 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 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 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 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 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 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 (e.g., food, light, living space) necessary for survival is limited. Therefore organisms must compete with each other for these resources. Darwin and the Theory for Evolution 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. an organism evolves traits that are beneficial, as well as traits that are neither harmful nor beneficial 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 Darwins 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 (cont) meiosis (reduction division) is special kind of cell division that forms haploid cells called gametes 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 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 organisms own genes that are present in the next generation 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 Evolution of New Species Modern species definition (cont) 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 temporal isolationthe time members of one species are ready to reproduce does not coincide with the time members of a related species reproduce Evolution of New Species biochemical isolationbiochemical or genetic differences between the gametes of 2 species prevent successful copulation from resulting in offspring isolating mechanisms that prevent successful reproduction following fertilization incompatible genes or biochemical differences can prevent a fertilized egg from developing further the hybrid offspring may survive but be infertile or poorly equipped to compete, dies out without reproducing Evolution of New Species Speciation: refers to mechanism by which new species arise 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 on each segment of the original population independently Evolution of New Species Classification: Bringing Order to Diversity Linneaus and the binomial system of naming binomial nomenclature: system 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 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 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 Classification: Bringing Order to Diversity