2. Biology EOC Class #4 Room 223 Mrs. Gleb

3. Class Four Plan!  Writing: Field Study Procedures  DNA  Evolution  Genetics  Practice Test Questions (if there is time!)

4. Writing on the EOC  You MUST write something on these sections!  These questions are where the most students lose points – do not skip them  Carefully review each writing question and underline the components that your answer should have

5. Types of Short Answer / Writing Questions  Field Study Procedure  Record environmental conditions  Identify 2 controlled variables  Identify manipulated variable (3 conditions)  Identify responding variable  Say RECORD data (not “measure” data)  Make your final step “repeat steps (list steps) two more times and average the data”

6. Procedures Students sometimes write conclusions or predictions instead of the steps for a procedure. Students sometimes miss the differences between controlled experiments and field studies when writing procedures. Many of those differences are defined by the bullets included with the item. For example, field studies include recording environmental conditions and describing the method for collecting data (e.g., a consistent sampling strategy). Students need to write procedures that use the manipulated (independent) and responding (dependent) variables given in the new experimental or field study question. Many students use the same responding variable as was used in the original scenario. A procedure that does not use the correct manipulated (independent) variable cannot answer the given investigative question and no points can be earned on the item.

7. Procedures Continued The manipulated (independent) and responding (dependent) variables do not need to be specifically named or listed (e.g., Manipulated variable is water temperature) in order to receive credit for them; the variables just need to be used correctly in the procedure to be credited. Sometimes students switch the identities of the manipulated and responding variables and contradict their procedure. Students need to be very clear about what they are measuring. Many students write “record the data,” “measure the data,” or “watch what happens and record the measurements” without actually stating the responding variable. They should write things like “record the number of organisms in the sample area,” “measure the height of the plant,” or “measure the time for seeds to germinate” to earn credit for the responding variable. Students are expected to include at least three conditions of the manipulated/independent variable for both controlled experiments and field studies.

8. 7

9. 8 DNA  DNA.  DNA is often called the blueprint of life.  In simple terms, DNA contains the instructions for making proteins within the cell.

10. 9 Watson & Crick’s Model

11. 10 DNA Why do we study DNA ? We study DNA for many reasons, e.g.,  its central importance to all life on Earth,  medical benefits such as cures for diseases,  better food crops.

12. 11 Chromosomes and DNA  Our genes are on our chromosomes.  Chromosomes are made up of a chemical called DNA.

13. 12 The Shape of the Molecule  DNA is a very long polymer.  The basic shape is like a twisted ladder or zipper.  This is called a double helix.

14. 13 The Double Helix Molecule  The DNA double helix has two strands twisted together.

15. 14 One Strand of DNA  The backbone of the molecule is alternating phosphates and deoxyribose sugar  The teeth are nitrogenous bases. phosphate deoxyribose bases

16. Nucleotides One deoxyribose together with its phosphate and base make a nucleotide. CC C O Phosphate O C C O -P O O O O O O O Nitrogenous base Deoxyribose

17. 16 One Strand of DNA  One strand of DNA is a polymer of nucleotides.  One strand of DNA has many millions of nucleotides. nucleotide

18. 17 Four nitrogenous bases  Cytosine C  Thymine T  Adenine A  Guanine G DNA has four different bases :

19. 18 Two Kinds of Bases in DNA  Pyrimidines are single ring bases.  Purines are double ring bases. C C C C N N O N C C C C N N N N N C

20. 19 Thymine and Cytosine are pyrimidines  Thymine and cytosine each have one ring of carbon and nitrogen atoms. C C C C N N O N cytosine C C C C N N O O thymine C

21. 20 Adenine and Guanine are purines  Adenine and guanine each have two rings of carbon and nitrogen atoms. C C C C N N N Adenine N N C C C C C N N O N Guanine N N C

22. 21 Two Stranded DNA  Remember, DNA has two strands that fit together something like a zipper.  The teeth are the nitrogenous bases but why do they stick together?

23. 22 C C C C N N O N C C C C N N O N N N C Hydrogen Bonds  The bases attract each other because of hydrogen bonds.  Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA.  The bonds between cytosine and guanine are shown here with dotted lines

24. 23 Hydrogen Bonds, Hydrogen Bonds, cont.  When making hydrogen bonds, cytosine always pairs up with guanine  Adenine always pairs up with thymine  Adenine is bonded to thymine here C C C C N N N N N C C C C C N N O O C

25. Chargraff’s Rule: Adenine and Thymine always join together  A T Cytosine and Guanine always join together  C G 24

26. 25 DNA by the Numbers  Each cell has about 2 m of DNA.  The average human has 75 trillion cells.  The average human has enough DNA to go from the earth to the sun more than 400 times.  DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun.

27. Evolution

28. Voyage of the Beagle  During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time.

29. Darwin’s Observations  Giant Tortoises of the Galápagos Islands

30. Darwin’s Observations  Variety of finches

31. Jean-Baptiste Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to changes in a species. Lamarck’s explanation of how evolution works was wrong, but it helped set the stage for Darwin’s ideas

32. Others that influenced Darwin’s ideas  Charles Lyell: explained that slow and gradual processes have shaped Earth’s geological features over long periods of time.  Thomas Malthus: Populations can grow much faster than the rate at which supplies of food or other resources can be produced.  Alfred Wallace: Described same basic mechanisms for evolutionary change that Darwin had proposed.

33. Darwin’s Two Main Points  Descent with modification: Descendants of earliest organisms accumulated adaptations to different ways of life.  Natural selection: The process by which individuals with inherited characteristics well-suited to the environment leave more offspring on average than other individuals

34. Darwin’s Book  The Origin of Species (1859)

35.  Natural selection: The process by which individuals with inherited characteristics well- suited to the environment leave more offspring on average than other individuals

36. Evidence of evolution Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in:  the fossil record,  the geographical distribution of living species  homologous structures of living organisms,  Vestigial structures,  Similarities in early development,  Molecular biology.

37. Fossil Record  Each layer of sedimentary rock represents a time period. Fossil in each layer represent organisms that lived when the layer was formed

38. Geographic Distribution of Living Species  Darwin decided that all Galápagos finches could have descended with modification from a common mainland ancestor.

39. When pre-New Zealand split of from Australia, a new specie of birds called the "Kaka" evolved from its parrot-like ancestor. Then as new mountain ranges are formed in pre-New Zealand, these birds further evolve into two distinct specie: Lowland Kaka and Alpine Kea. Later, when pre-New Zealand split into two islands (which is now modern day New Zealand), the Lowland Kaka evolved into the North Island Kaka and the South Island Kaka. EXAMPLE OF GEOGRAPHICAL DISTRIBUTION

40. Homologous Body Structures  Structures that have different mature forms but develop from the same embryonic tissues are called homologous structures.  Similarities and differences in homologous structures help biologists group animals according to how recently they last shared a common ancestor.

42. Not all homologous structures serve important functions. The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. These organs are called vestigial organs.

43. Similarities in Embryology  The early stages, or embryos, of many animals with backbones are very similar.  The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates.

45. What about DNA  The use of Genetics and the knowledge of DNA has allowed for analysis of the similarities and differences between organisms. Common DNA sequences may support the theory that they share a common ancestor.

54. Mendel + Darwin Genetics Evolutionary biology Change within populations

55. What is the gene pool of a population?  The sum total of all the alleles (alternative forms of genes) in all individuals that make up a population.

56. Microevolution  Evolution based on genetic changes  A generation-to-generation change in the frequencies of alleles within a population

57. Hardy-Weiberg equilibrium  The frequency of alleles in the gene pool of a population remain constant over time (in contrast to microevolution).  This equilibrium is not maintained in nature.

58. What mechanisms can change a gene pool?  Genetic Drift (Chance)  Bottleneck effect  Founders effect  Natural selection (Chance & sorting)  Gene flow  Mutation

59. Genetic Drift Change in a gene pool of a population due to chance

60. Effects of genetic drift in small populations: The bottleneck Effect Natural disasters

61. And The Founders Effect  A few individuals colonize an isolated island, lake, or some other new habitat.

62. Gene Flow  Exchange of genes with other populations  Interbreeding increases variation in the population’s gene pool

63. Mutations  Mutations carried by gametes enter the gene pool

64. What leads to adaptation?  Natural selection – a blend of chance and sorting  Chance - mutation & sexual recombination of alleles lead to genetic variation in a population  Sorting – differences in reproductive success among members of the varying population  Genetic drift, gene flow, and mutation cause microevolution or changes in allele frequencies, but not adaptation

65. Genetics

66.  Scientific Study of heredity (how traits are passed on to future generations)  Trait: specific characteristics of an individual  Hybrid: The offspring of crosses between parents of different traits  P1 + P1 = F1 / F1 + F1 = F2  P is parent generation, F1 is first generation, F2 is second generation

67. Genes & Alleles  Genes determine traits  Different forms of a gene are called alleles  Principle of dominance  Some alleles are dominant, others are recessive

68. Principle of Segregation  Gametes (sex cells)  During gamete formation, the alleles for each gene segregate from each other  Each gamete carries only one allele for each gene

69. Punnet Squares

70.  Two identical alleles are called homozygous  Example: tt or TT  Two different alleles are called heterozygous  Example: tT

71. Phenotype vs Genotype  Two hybrids can have the same phenotype (physical characteristics), but different genotypes (genetic make up) because of dominate and recessive genes

72. Incomplete Dominance  Sometimes one allele is not completely dominate over another

73. Codominance  In codominance, both alleles are expressed