Evolution and Adaptation: The Changing Face of Life

1. BSC 2010 - Exam I Lectures and Text Pages • I. Intro to Biology (2-29) • II. Chemistry of Life • Chemistry review (30-46) • Water (47-57) • Carbon (58-67) • Macromolecules (68-91) • III. Cells and Membranes • Cell structure (92-123) • Membranes (124-140) • IV. Introductory Biochemistry • Energy and Metabolism (141-159) • Cellular Respiration (160-180) • Photosynthesis (181-200)

2. Figure 1.17 Evolution and Adaptation: Properties of Life • Evolution accounts for life’s unity and diversity • The history of life • Is a saga of a changing Earth billions of years old

3. Evolution and Adaptation: Properties of Life 3 basic themes: 1) variation: in the genetic makeup of individuals 2) adaptation: of traits to the environment 3) natural selection: leads to differential reproduction: those organisms better adapted produce more offspring

4. Figure 1.18 The evolutionary view of life • Came into sharp focus in 1859 when Charles Darwin published On the Origin of Species by Natural Selection • He described the theory of natural selection. Prior to this, many scientists and scholars believed in evolution, but there was no solid idea about how it worked.

5. Figure 1.19 The Origin of Species articulated two main points • Descent with modification • Natural selection

6. Theory of Natural Selection: requires 3 basic conditions: • 1. Individuals vary (all organisms are not equal) • 2. There is a struggle for limited resources (i.e. competition) • 3. Organisms have differential success at reproduction. Evolution and Adaptation are key features of life. Evolution provides evidence that life responds to changes in the environment.

7. Population of organisms Overproduction and struggle for existence Hereditary variations Differences in reproductive success Evolution of adaptations in the population Figure 1.20 He proposed “Natural Selection” As the mechanism for evolutionary adaptation of populations to their environments

8. 1 Populations with varied inherited traits 2 Elimination of individuals with certain traits. 3 Reproduction of survivors. Figure 1.21 4 Increasing frequency of traits that enhance survival and reproductive success. Natural selection is the evolutionary process that occurs • When a population’s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others

9. Figure 1.22 The products of natural selection Are often exquisite adaptations of organisms to the special circumstances of their way of life and their environment

10. Evolution is change over time within the original gene pool. • It is possible to have change through random mutations, without natural selection, but usually it is beneficial mutations that are enhanced through natural selection: Some mutations confer adaptive value. • Example: A mutation may have the effect of allowing a bacterium to survive or resist a bacterial spray or an antibiotic. That bacterium survives, and produces offspring, passing on the resistance mutation, so in the next generation more of the bacteria are resistant. Thus a resistant strain of bacteria evolves, and soon we find it more and more difficult to eliminate harmful bacteria. • So, a mutation can create variation on which natural selection then acts. The environment itself does not create change. Natural selection leads to greater reproduction of well-adapted individuals, which leads to evolution (change in gene frequency over time).

11. The Tree of Life • Many related organisms • Have very similar anatomical features, adapted for their specific ways of life • Such examples of kinship • Connect life’s “unity in diversity” to Darwin’s concept of “descent with modification”

12. Large ground finch Large tree finch Smallground finch Large cactus ground finch Camarhynchuspsitacula Greenwarbler finch Graywarbler finch Geospiza magnirostris Geospizafuliginosa Mediumtree finch Sharp-beaked ground finch Woodpecker finch Mediumground finch Geospiza conirostris Certhideaolivacea Certhideafusca Geospiza difficilis Camarhynchuspauper Cactusground finch Cactospizapallida Mangrovefinch Geospiza fortis Small tree finch Geospizascandens Camarhynchusparvulus Cactospiza heliobates Vegetarianfinch Cactus flowereater Seed eater Seed eater Platyspizacrassirostris Insect eaters Bud eater Ground finches Tree finches Warbler finches Common ancestor fromSouth American mainland Figure 1.23 Darwin proposed that natural selection Could enable an ancestral species to “split” into two or more descendant species, resulting in a “tree of life”

13. Each species is a twig on a branching tree of life • Extending back in time through ancestral species more and more remote • All of life • Is connected through its long evolutionary history

14. Evolution: is a change in gene frequency over time. • It is the result of two main processes: 1. natural selection: “survival of the fittest”. Some organisms, due to the characteristics of their environment, will survive and reproduce more than others. e.g. Galapagos finches- some had larger beaks than others when a drought hit the islands, leaving only thick, hard seeds. Only the birds with large beaks were able to eat, the others starved. Therefore, the big-beaked birds had the energy to reproduce and the next generation all had large beaks. 2. adaptation: the process of becoming better suited to the environment. Can happen through natural selection or through genetic drift (random change due to mutation or circumstances). • * The word “adaptation” can also be used to describe a trait of a particular organism that has arisen through natural selection. e.g. a giraffe’s long neck is an adaptation for eating leaves of tall trees.

15. Table 1.1 Eleven themes that unify biology

16. BSC 2010 - Exam I Lectures and Text Pages • I. Intro to Biology (2-29) • II. Chemistry of Life • Chemistry review (30-46) • Water (47-57) • Carbon (58-67) • Macromolecules (68-91) • III. Cells and Membranes • Cell structure (92-123) • Membranes (124-140) • IV. Introductory Biochemistry • Energy and Metabolism (141-159) • Cellular Respiration (160-180) • Photosynthesis (181-200)

17. Chemical Foundations of Biology An understanding of the workings of the cell and the physiology of multicellular organisms requires an understanding of chemistry. Living organisms are chemical systems.

18. The bombardier beetle uses chemistry to defend itself Figure 2.1

19. Matter, Elements, Molecules, Compounds Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter, which is anything that takes up space and has mass. Element: basic unit of matter, cannot be subdivided into simpler substances (by ordinary chemical means). The smallest unit of an element is a single atom. Molecule: a substance composed of more than one atom.

20. + Sodium Chloride Sodium Chloride • A compound • Is a substance consisting of two or more elements combined in a fixed ratio • Has characteristics different from those of its elements Figure 2.2

21. Matter • All matter is made up from 92 naturally occurring elements. • Living matter requires only 25 of these 92 elements. These are the “Essential Elements of Life”.

22. Essential Elements of Life Carbon, hydrogen, oxygen, and nitrogen (CHON) account for 96% of living matter. A few other elements make up the remaining 4%. • Trace elements • Are required by an organism in only minute quantities

23. (a) Nitrogen deficiency (b) Iodine deficiency The effects of essential element deficiencies Figure 2.3

24. Element’s properties depend on structure of its atoms • Each element • Consists of a certain kind of atom that is different from those of other elements • An atom • Is the smallest unit of matter that still retains the properties of an element

25. Subatomic Particles • Atoms of each element • Are composed of even smaller parts called subatomic particles • Relevant subatomic particles include • Neutrons, which have no electrical charge • Protons, which are positively charged • Electrons, which are negatively charged

26. Cloud of negative charge (2 electrons) Electrons Nucleus (a) This model represents the electrons as a cloud of negative charge, as if we had taken many snapshots of the 2 electrons over time, with each dot representing an electron‘s position at one point in time. (b) In this even more simplified model, the electrons are shown as two small blue spheres on a circle around the nucleus. • Protons and neutrons are found in the atomic nucleus • Electrons surround the nucleus in a “cloud” Figure 2.4

27. Atomic Number and Atomic Mass • Atoms of the various elements • Differ in their number of subatomic particles • The atomic number of an element • Is the number of protons • Is unique to each element Example: Carbon has an atomic number of 6. If you know the atomic number, you know the element. Usually, in naturally occurring elements, the number of protons = the number of electrons. Therefore the atom has a neutral charge. The properties of atoms are determined by the number and arrangement of their electrons.

28. The mass number of an element • Is the sum of protons plus neutrons in the nucleus of an atom • Is an approximation of the atomic mass of an atom • One mole of protons or neutrons has a mass of one gram.

29. Isotopes – atoms of an element may occur in different forms • Isotopes of a given element • Differ in the number of neutrons in the atomic nucleus • Have the same number of protons

30. Radioactive isotopes • Are unstable and spontaneously give off particles and energy • Radioactivity has negative effects, as when it causes cancer, but also has positive uses, as when it is used as a marker in biological molecules.

31. Radioactive isotopes Cancerous throat tissue Figure 2.6 • Can be used in biology

32. Atomic structure of atoms determines how they interact. Electron orbitals • Electrons are located in specific energy levels around the nucleus. You will need to know the number of electrons in the outermost (reactive) energy level for the different elements. The total number of electrons = the total number of protons (atomic number) • DO NOT ASSUME A CHARGE on any atom unless you see a charge symbol.

33. Third energy level (shell) Second energy level (shell) Energy absorbed First energy level (shell) Energy lost Atomic nucleus (b) An electron can move from one level to another only if the energy it gains or loses is exactly equal to the difference in energy between the two levels. Arrows indicate some of the step-wise changes in potential energy that are possible. Figure 2.7B • Energy levels • Are represented by electron shells

34. Helium 2He Atomic number 2 He 4.00 Hydrogen 1H Element symbol Atomic mass First shell Electron-shell diagram Beryllium 4Be Carbon 6C Oxygen 8O Neon 10Ne Lithium 3Li Boron 3B Nitrogen 7N Fluorine 9F Second shell Aluminum 13Al Chlorine 17Cl Argon 18Ar Sulfur 16S Sodium 11Na Magnesium 12Mg Silicon 14Si Phosphorus 15P Third shell Figure 2.8 • The periodic table of the elements • Shows the electron distribution for all the elements

35. Valence electrons • Are those in the outermost, or valence shell • Determine the chemical behavior of an atom Figure 4.4

36. Electron orbitals. Each orbital holds up to two electrons. x Y 1s orbital 2s orbital Three 2p orbitals 1s, 2s, and 2p orbitals Z Electron-shell diagrams. Each shell is shown with its maximum number of electrons, grouped in pairs. (b) Second shell (maximum 8 electrons) (a) First shell (maximum 2 electrons) (c) Neon, with two filled shells (10 electrons) Figure 2.9 • Each electron shell • Consists of a specific number of orbitals

37. Bonding Rules • 1. Interactions are based on exchange or rearrangement of electrons in the outer shell (valence shell), also called valence electrons.  (valence # is # of e- needed to fill outer shell). • 2.Stable atoms have a full outer shell. • 3.Atoms that have 1, 2, or 3 valence e- tend to lose them in reactions with atoms that have 5, 6, or 7, and thus form + ions. • 4.Atoms that have 5, 6, or 7 valence e- tend to gain those lost by those with 1, 2, or 3, and thus form - ions. • 5.Atoms with 4 valence e- tend to share = covalent bonds