Chapter 5 Biological Concepts

1. Chapter 5 Biological Concepts

2. 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

3. 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.

7. The binomial system of nomenclature uses two words, the genus and the species epithet, to identify an organism. • Homo sapiens or Homosapiens - human • Callinectus sapidus or Callinectussapidus – blue crab • Common names can be confusing, the scientific name allows you to know the organism no matter what language you speak

8. 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

9. 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

10. 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

11. Carbohydrates • Contain C, H and O, frequently in a 1:2:1 ratio • CH2O - thus the name carbohydrate (carbon water)

12. 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)

13. 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

15. 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

17. 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, three-dimensional protein molecules • Functions of proteins • compose primary structural components of animals: muscles and connective tissue • enzymes—biological catalysts • transport or store chemicals

19. 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

20. 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

22. 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)

23. 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

24. Types of Cells • Prokaryotic cells (bacteria, archaeans) • lack a nucleus and membrane-bound organelles • prokaryotes (prokaryotic organisms) are always unicellular

25. Eukaryotic cells (protists, fungi, plants, animals) • have a well-defined nucleus and many membrane-bound organelles • eukaryotes may be uni- or multi-cellular

29. Organelles • Have specific functions within cell • Nucleus • Mitochondria • Chloroplasts • Endoplasmic reticulum • Lysosomes • vacuoles

30. Energy Transfer in Cells

31. 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

32. 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

33. 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

35. 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

37. 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

39. 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

40. 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

41. 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

42. 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

43. Darwin and the Theory for Evolution • Four basic premises of Darwin’s theory • All organisms produce more offspring than can possibly survive to reproduce. • There is a great deal of variation in traits among individuals in natural populations. Many of these variations can be inherited. • 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. • 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.

44. 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

45. 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.

46. 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

49. 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