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Human Biology, Behavior, and Evolution Notes PART 2 [COMPLETE]: 90% on final!

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Boston University
CAS AN 102

Natural Selection 1.There must be variation within a population 2.Most variation is inherited (heritability) 3.Over-reproduction leads to competition and a struggle for existence ⁃ Due to variation, some individuals are better able to survive and reproduce than others (differential reproductive success) ⁃ Introduced by Malthus (1838) Variation, heritability, and differential reproductive success lead to the retention of traits that improve survival or reproduction Reproductive success: Leaving more copies of your genes in subsequent generations than do others Fitness: Ability of an individual to contribute genetic material to subsequent generations Adaptation: A feature or trait that evolved via natural selection to perform a specific task that directly or ultimately leads to reproduction or survivorship Evolution in action ⁃ Medium ground finch on Daphne Major ⁃ Drought of 1977 ⁃ Beak depth of 1978 greater than beak depth of 1976 (drought washed out smaller seeds) Sexual Selection 1.Inter-sexual choice 2.Intra-sexual competition 3.Inter-sexual coercion (proposed by Barbara Smuts) Primary sex differences (genitals, xy) Secondary sex differences (size, color, behavior, physiology) Idea of female choice rejected by Victorians/view of females as sexually passive Wallace attributed peacock tail "superabundant energy of males" Birds of paradise show female choice ⁃ Males evolve colorful plumage because there are no predators Orangutans (males double size of female, males fight to death for females, females prefer prime flanged males, forced copulations) Genetics Cellular and molecular genetics: study of genetics at level of cells and the DNA molecule Classical or Mendelian genetics: how traits are passed between generations through pedigree Population genetics: examines variation within and between populations of one species Phylogenetics: determining evolutionary relationships betewen species Behavioral genetics: examines how animal behavior is influenced by genetics Homunculus in sperm: person inside Walter Flemming (1882) -Discovered paired chromosomes inside the cell nucleus and mitosis -Hypothesized that inheritance is passed on through chromosomes, one from each parent -Confirmed by discovery of gametes contain only set of chromosomes -When gametes unite the zygote contains two complete sets of chromosomes Wilhelm Johannsen (1857-1927) -Coined term gene to describer the unit of inheritance on chromosomes Discovery of DNA in 1953 -By James Watson, Maurice Wilkins, and Francis Crick with help from Rosalind Franklin Cells ▪ Haploid: Cell with one copy of each chromosome (gametes) ▪ Diploid: Containing pairs of homologous chromosomes, one of each pair is inherited from each parent ▪ Prokaryotes (no nucleus, single-celled such as bacteria and blue-green algea, haploid) ▪ Eukaryotes (have nucleus, appears 1.2 billion years ago) ▪ Organelles ▪ -DNA in nucleus and mitochondria ▪ -Nucleus, cytoplasm ("glue" in cell), mitochondria (energy), ribosomes (make protein, part of the Rough Endoplsmic Reticulum), nuclear envelope, plasma membrane (outside skin) ▪ Somatic cells (Tissue cells, diploid, with 46 chromosomes) ▪ Gamete cells (Reproductive cells, ova and sperm) ▪ Stem cells (Can be formed into different type of somatic cells) DNA Replication • Homologous chromosomes not normally paired up • Cell interphase: the period when a cell is not actively dividing (cells in interphase most of the time) • Chromatin: when DNA is dispersed and uncoiled in the nucleus • Replication happens when DNA is in chromatin form • Enzymes break the DNA bonds and it unzips down the middle • Unattached nucleotides pair with the complementary nucleotide on each strand • Chromosomes begin to form ⁃ Chromatin condenses into chromosomes • DNA condenses around proteins called histones • Two identical strands of DNA join together at the centromere • Chromatids form, doubles chromosome is composed of two identical chromatids ⁃ Now there are 46 double stranded chromosomes Mitosis: somatic cell replication (diploid to diploid) ▪ Nuclear membrane disappears ▪ Chromatids align on center of cell ▪ Chromatids split apart at the centromeres and duplicate chromosomes move to either end of the cell ▪ Cell pinches into two cells Meiosis: sex cell production (diploid to haploid) ▪ Produces 4 haploid cells ▪ DNA replicates ▪ Before first division chromatids match up with their homologous chromosome forming a tetrad ▪ Genetic material is exchanged between homologous chromosomes through recombination ▪ Recombination: two strands of genetic material broken and joined to a homologous chromosome ⁃ Leads
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