Biology Review


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First lecture for Drury Ava Campus Spring 2010

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  • Biology is the study of living organisms. Zoology focuses on the Kingdom Animalia. In this course we’ll be studying the diversity of animals on our planet, how they are related, how they work, and how they interact with each other. Zoologists strive to understand: The origin of animal diversity. How animals perform basic life processes. How they are able to inhabit various ecosystems. Principles of modern zoology are derived from: Laws of physics and chemistry Scientific method Because life shares a common evolutionary origin, principles learned from the study of one group often pertain to other groups as well.
  • Introduction of evolutionary theory into animal taxonomy changed taxonomist’s role from one of classification to systematization. Taxonomy produces a formal system for naming and classifying species to illustrate their evolutionary relationship. Classification denotes the construction of classes. Grouping of organisms that possess a common feature called an essence used to define the class. Taxonomy Formal system for naming and classifying species. Systematics Broader science of classifying organisms based on similarity, biogeography, etc. Systematic zoologists have three goals: To discover all species of animals. To reconstruct their evolutionary relationships. To classify animals according to their evolutionary relationships. In classification Taxonomist asks whether a species being classified contains the defining feature of a particular taxonomic class. In systematization Taxonomist asks whether the characteristics of a species confirm or reject the hypothesis that it descends from the most recent common ancestor of a particular taxon. Systematization places groups of species into units of common evolutionary descent. Character variation is used to diagnose systems of common descent. No requirement that an essential character be maintained throughout the system for its recognition as a taxon.
  • All animals are placed in Kingdom Animalia. Names of animal groups at each rank in the hierarchy are called taxa (taxon). Each rank can be subdivided into additional levels of taxa. Superclass, suborder, etc.
  • Defining a species can be difficult. Criteria: Common descent The smallest distinct groupings of organisms sharing a pattern of descent. Morphological & molecular techniques Members of a species must form a reproductive community that excludes other species.
  • This common history can be traced backward through time from the diverse forms observed today and in the fossil record to their common ancestor that arose in the atmosphere of the primitive earth. Life's history of descent with modification gives it an identity and continuity that separates it from the nonliving world. Clicker Case!
  • Animals share common environments and ecological principles that we need to study to learn how they interact together.
  • Prokaryotic cells – no nucleus or other membrane-bound organelles. Kingdom Archaebacteria Kingdom Eubacteria Eukaryotic cells – do have nucleus and membrane-bound organelles. Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia
  • The plasma membrane surrounds the cell. The nucleus is the largest organelle. Double layered nuclear envelope .
  • Microtubules are larger tubular structures composed of the protein tubulin . Move chromosomes during cell division. Part of the structure of cilia & flagella. – important in zoology! Cilia & flagella are motile extensions of the cell surface. In many single celled organisms they are a source of locomotion. In multicellular animals they usually sweep material past the fixed cell. Nine pairs of microtubules enclose a central pair. At the base is a basal body - identical to a centriole.
  • Atom  molecule  membranes  organelles  cells  tissues  organs  organ systems  organism
  • Powerful theories that guide extensive research are called paradigms. The refutement and replacement of a paradigm is known as a scientific revolution. Two major paradigms that guide zoological research: Chapters 3 and 4 (In opposite order)
  • Darwin knew that some traits were heritable, but he didn’t have an understanding of the mechanism of heredity.
  • Mendel chose peas to study inheritance because they possess several contrasting traits without intermediates. Green vs. yellow peas Tall vs. short plants Wrinkled vs. smooth peas Purple vs. white flowers
  • Evolution – a change in the genetic composition of a population over time. A change in the frequency of certain alleles. On a larger scale, evolution can be used to refer to the gradual appearance of all biological diversity. The Origin of Species focused attention on the diversity of life, similarities as well as differences, and the adaptations organisms have for particular environments. Charles Darwin presented evidence that many modern organisms are descended from ancestral species that were different.
  • Philosophers Empedocles and aristotle described concept of change in living organisms over time. Lamarck French zoologist was the first to suggest an explanation for evolution. Inheritance of acquired characteristics – driven by need Didn’t hold up to testing giraffe example often quoted by creationists, but not ever widely accepted.
  • Natural forces could explain the formation of fossil-bearing rocks. Lyell concluded the age of the earth must be millions of years. He stressed the gradual nature of geological changes.
  • Darwin started out on a five year trip around the world aboard the Beagle in 1831. He was 22. As ship’s naturalist he spent his time on shore collecting thousands of plant and animal specimens and making important observations. During the voyage he read Lyell’s Principles of Geology . He had Lyell’s ideas in mind as he traveled and observed the geology of South America.
  • He experienced an earthquake in Chile and observed that the coastline had risen several feet. He also found marine fossils high in the Andes Mountains. Darwin concluded that the mountains were formed by a series of such earthquakes. Darwin saw that the plants and animals that he found in temperate areas of South America were more similar to tropical South American species than they were to temperate European species. Darwin became interested in the geographic distribution of organisms after visiting the Galapagos Islands.
  • Wallace independently developed a theory of natural selection. He sent his manuscript to Darwin, spurring him to finally publish his ideas. Both ideas were presented to the Linnean Society in 1858. Darwin finished On the Origin of Species and published it in 1859.
  • After returning, Darwin realized that adaptation to the environment and the origin of new species were closely linked processes. Galapagos finch species have evolved by adapting to specific conditions on each island. After reading a paper by Thomas Malthus concerning the fact that human populations increase faster than limited food resources, Darwin noticed the connection between natural selection and this ability of populations to overreproduce. Those that survive may have heritable traits that increased their chances of survival. They will pass those traits on. The frequency of those traits will increase.
  • Natural Selection – Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Natural selection requires: Variation within the population. This variation must be heritable . Organisms with a particular variation will have more offspring. Over time, these successful variations will spread through the population. Darwin presented a mechanism for evolution – natural selection . Organisms that are in some way more successful at reproduction will pass on more of their genes. Over time the traits responsible for that success will become widespread in the population. This theory holds up very well!!
  • Natural selection occurs when organisms with particular heritable traits have more offspring that survive & reproduce. Natural selection can increase the adaptation of an organism to its environment. A Flower mantid vs. a stick mantid When an environment changes, or when individuals move to a new environment, natural selection may result in adaptation to the new conditions. Sometimes this results in a new species. Individuals do not evolve; populations evolve. Evolution is measured as changes in relative proportions of heritable variations in a population over several generations Natural selection can only work on heritable traits. Acquired traits are not heritable and are not subject to natural selection. Environmental factors are variable. A trait that is beneficial in one place or time may be detrimental in another place or time.
  • Artificial selection – people selectively breed organisms with desired traits. Darwin noticed that considerable change can be achieved in a short period of time.
  • Fossils are remnants of past life preserved in the earth. Complete remains – insects in amber. Petrified skeletal parts infiltrated with silica or other minerals. Or traces of organisms such as molds, casts, impressions, trackways, or fossilized excrement.
  • Fossils provide support for the idea that life changes through time. Fossil intermediates Whales descended from land mammals. Birds descended from one branch of dinosaurs. The oldest fossils are of prokaryotes.
  • The phrase “descent with modification” summarizes Darwin’s view of how Evolution works. All organisms descended from common ancestor. Similar species have diverged more recently. Homology – when similar structures result from shared ancestry. Homologous structures – variations on a structural theme that was present in a common ancestor. Example – vertebrate forelimbs have different functions, but share the same underlying structure.
  • Vestigial organs – remnants of structures that served important functions in an ancestor. Remnants of pelvis and leg bones in snakes Appendix in humans
  • Natural selection explains why organisms are constructed to meet the demands of their environments. Adaptation results when the most favorable variants accumulate over evolutionary time.
  • Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages. Analogous structures or molecular sequences that evolved independently are also called homoplasies . A shared primitive character : Is a homologous structure that predates the branching of a particular clade from other members of that clade. Is shared beyond the taxon we are trying to define. Example – mammals all have a backbone, but so do other vertebrates.
  • A shared derived character is an evolutionary novelty unique to a particular clade. All mammals have hair, and no other animals have hair. The nested hierarchy of clades can be represented as a cladogram that is based on shared synapomorphies. Polarity is determined by using outgroup comparison . An outgroup is closely related, but not part of the group being examined (the ingroup ). If a character is found in both the study group and the outgroup, it is considered ancestral for the study group. Character groups found in the study groups but not the outgroups are derived .
  • A phylogenetic tree is another way of representing evolutionary relationships. Branches represent real lineages that occurred in the evolutionary past. Includes information about ancestors, duration of evolutionary lineages, amounts of evolutionary change that has occurred.
  • Common Descent – All forms of life descended from a common ancestor through a branching of lineages. Life’s history has the structure of a branching evolutionary tree, known as a phylogeny Serves as the basis for our taxonomic classification of animals Descent with modification. Supported by molecular work. A major goal of systematics is to infer the evolutionary tree or phylogeny – the evolutionary history of a species or group of related species. Phylogenies are inferred by identifying organismal features, characters , that vary among species. Morphological Chromosomal Molecular Behavioral or ecological
  • Variation exists within any population. When natural selection acts to favor one trait over another that trait will increase in the population . The population has evolved, not any one individual. Population Genetics – the study of how populations change over time. Dependent on both Darwin’s theory of natural selection and Mendel’s laws of inheritance. All heritable traits have a genetic basis, some are controlled by multiple genes – not as simple as in Mendel’s studies.
  • Population – a localized, interbreeding group of individuals of a particular species. Separate populations of a species may be isolated from each other. Sometimes the populations overlap, but little interbreeding occurs.
  • Carrying Capacity only allows a certain number of individuals to survive in an ecosystem/habitat.
  • Gene mutations result in an alteration of the sequence of bases in the DNA. Harmful Neutral Beneficial New genes or alleles only result by mutations. Mutations are changes in the nucleotide sequence of DNA. Beneficial mutations of any kind are very rare. Mutations that alter gene number or sequence are almost always harmful.
  • Sexual recombination is a much more common way of producing variation in populations. Reshuffling of allele combinations already present in the population is how variation is maintained in populations. Sexual reproduction rearranges alleles into fresh combinations every generation. When natural selection is occurring, some individuals are having better reproductive success than others. Alleles are being passed to the next generation in frequencies that are different from the current generation. When natural selection is occurring, some individuals are having better reproductive success than others. Alleles are being passed to the next generation in frequencies that are different from the current generation.
  • The smaller the sample, the greater the chance of deviation from expected results. These random deviations from expected frequencies are called genetic drift . Allele frequencies are more likely to deviate from the expected in small populations. Which allele was lost is due to random chance. Over time, drift tends to reduce genetic variation through random loss of alleles.
  • Sometimes a catastrophic event can severely reduce the size of a population. The random assortment of survivors may have drastically different allele frequencies. Bottleneck effect
  • Cheetahs are very inbred. They are so inbred, that genetically they are almost identical. The current theory is that they became inbred when a "natural" disaster dropped their total world population down to less than seven individual cheetahs - probably about 10,000 years ago . They went through a " Genetic Bottleneck ", and their genetic diversity plummeted. They survived only through brother-to-sister or parent-to-child mating. The actions of people sometimes cause bottlenecks in other species. N. California elephant seal population reduced to 20-100 individuals in the 1890s. Current population > 30,000. Variation drastically reduced – 24 genes with 1 allele.
  • Founder effect – When a small group of individuals becomes separated from the population and form a new population, the allele frequencies in their gene pool may be different than the original population. a type of genetic drift
  • The population can gain or lose new alleles through gene flow . When individuals move into or out of a population, they may carry the only copy of certain alleles in the gene pool with them. Gene flow usually reduces differences between populations. Variation in a population is always present. Heritable variation is the raw material of natural selection.
  • Stabilizing – removes the extremes. The average is the most favorable and both extremes are eliminated. Directional – variants at one of the extremes are favored. One trait is favored and the population shifts to one side or the other Disruptive – variants at both extremes are favored. The average is least favorable and the average is eliminated. Can separate the population into two groups which eventually may never interbreed. Also known as resource partitioning.
  • Not all genetic variation is heritable. Environmental influences sometimes effect phenotype. Bright colors emerge in spring, dark colors emerge in late summer
  • Different versions of discrete characters are called morphs . When a population has two or more morphs that are common in the population, it is called polymorphic . This is phenotypic polymorphism They are not a different species, just a different color.
  • Allopatric (another land) populations occupy separate geographic areas. Separated geographically, but able to interbreed if brought together. Over time, reproductive barriers may evolve so that they could not interbreed. Allopatric speciation The geographical separation can arise in two ways: Vicariant speciation is initiated when climatic or geological changes fragment a species’ habitat, forming impenetrable barriers. Founder events occur when a small number of individuals disperse to a distant place where no other members of their species exist.
  • Parapatric Speciation – geographically intermediate between allopatric and sympatric speciation. Two species are parapatric if their geographic ranges are primarily allopatric but make contact along a borderline that neither species successfully crosses.
  • Sympatric (same land) speciation occurs when speciation occurs in one geographic area – a lake for example. Individuals within the species become specialized on a food type, shelter, part of the lake etc. Eventually reproductive barriers evolve.
  • Habitat - Place or set of environmental conditions where a particular organism lives. Ecological Niche - Description of the role a species plays in a biological community, or the total set of environmental factors that determines species distribution. Generalists - Broad niche Specialists - Narrow niche
  • Law of Competitive Exclusion - No two species will occupy the same niche and compete for exactly the same resources for an extended period of time. One will either migrate, become extinct, or partition the resource and utilize a sub-set of the same resource. Given resource can only be partitioned a finite number of times.
  • resource partitioning - groups of individuals become specialized to utilize sub-sets of the same resource radiative evolution - divergence from common ancestor into two or more species
  • A predator is an organism that feeds directly upon another living organism, whether or not it kills the prey in doing so. Prey most successfully on slowest, weakest, least fit members of target population. Reduce competition, population overgrowth, and stimulate natural selection. Co-evolution Keystone Species - A species or group of species whose impact on its community or ecosystem is much larger and more influential than would be expected from mere abundance. Often, many species are intricately interconnected so that it is difficult to tell which is the essential component.
  • Interspecific - Competition between members of different species. Intraspecific - Competition among members of the same species. Often intense due to same space and nutritional requirements. Territoriality - Organisms defend specific area containing resources, primarily against members of own species. Resource Allocation and Spacing
  • Symbiosis - Intimate living together of members of two or more species. Commensalism - One member benefits while other is neither benefited nor harmed. Cattle and Cattle Egrets Mutualism - Both members benefit. Lichens (Fungus and Cyanobacterium) Parasitism - One member benefits at the expense of other. Humans and Tapeworms
  • Woese, Kandler and Wheelis proposed three monophyletic domains above kingdom level—Eucarya, Bacteria and Archaea—based on ribosomal RNA sequences.
  • Sexual selection – natural selection for mating success. May result in sexual dimorphism – differences between the sexes. Secondary sexual characteristics – not directly involved in reproduction.
  • Intrasexual selection – selection within the same sex – results when individuals of one sex are competing with each other for members of the other sex. Features that make the male a better fighter or more intimidating to other males would be favored.
  • Intersexual selection – mate choice – individuals of one sex are choosy in selecting a mate. Features that make an individual more attractive to the opposite sex would be favored. Showiness that results from mate choice can be risky. Flashy tails of guppies make them more visible to predators. Benefits of finding a mate outweigh potential costs. Showiness may reflect overall health.
  • Reproduction is one of the ubiquitous properties of life. Evolution is inextricably linked to reproduction. Two modes of reproduction are recognized: Asexual Sexual
  • Asexual reproduction – the production of offspring whose genes all come from one parent without the fusion of egg and sperm. Usually diploid eggs are produced by mitosis which then develop directly. Bacteria and many protozoa can reproduce by binary fission – separating into two or more individuals approximately the same size. Budding is a form of asexual reproduction where new individuals form as offshoots of a parent. The offspring may separate or remain attached to form colonies.
  • Freshwater sponges release specialized groups of cells called gemmules that can grow into new individuals. Fragmentation results when an organism’s body is broken into several pieces and each piece grows into a new organism. Regeneration – the regrowth of lost body parts. Fragmentation occurs in some sponges, cnidarians, polychaete annelids, tunicates. Sea stars can regenerate lost limbs, but only species in the genus Linckia can form new individuals from broken arms.
  • Animals living far from members of their own species can reproduce without having to search for a mate. Numerous offspring quickly – ideal for colonizing a new area. Advantageous in a stable, favorable environment because it reproduces a successful genotype precisely.
  • Sexual reproduction – the production of offspring by the fusion of haploid gametes (eggs & sperm) from two parents to form a diploid zygote (fertilized egg). Dioecious Gametes arise by meiosis. Genetic variability is increased by the random combinations of genes from the parents. Generally involves two parents. Special germ cells unite to form a zygote. S exual reproduction recombines parental characters. A richer, more diversified population results. In haploid asexual organisms mutations are expressed and selected quickly. In sexual reproduction a normal gene on the homologous chromosome may mask a gene mutation. Why do so many animals reproduce sexually rather than asexually? The costs of sexual reproduction are greater than asexual methods: More complicated. Requires more time. Uses more energy. The cost of meiosis to the female is passage of only half of her genes to offspring. Production of males reduces resources for females that could produce eggs. Many invertebrates with both sexual and asexual modes enjoy the advantages of both.
  • Biology Review

    1. 1. Zoology Review of Biology concepts.
    2. 2. The Science of Zoology <ul><li>Zoology is the study of animal life. </li></ul>
    3. 3. Classification <ul><li>Taxonomy </li></ul><ul><li>Systematics </li></ul>
    4. 4. Linnaeus and Classification <ul><li>Carolus Linnaeus designed our hierarchical classification scheme. </li></ul><ul><ul><li>Kingdom </li></ul></ul><ul><ul><li>Phylum </li></ul></ul><ul><ul><li>Class </li></ul></ul><ul><ul><li>Order </li></ul></ul><ul><ul><li>Family </li></ul></ul><ul><ul><li>Genus </li></ul></ul><ul><ul><li>Species </li></ul></ul>
    5. 5. Linnaeus and Classification <ul><li>Binomial nomenclature is the system Linnaeus used for naming species. </li></ul><ul><ul><li>Genus and species </li></ul></ul><ul><ul><li>Names are latinized and italicized, only the genus is capatilized. </li></ul></ul><ul><ul><li>Sitta carolinensis </li></ul></ul>
    6. 6. Linnaeus and Classification <ul><li>A trinomial name includes a subspecies epithet. </li></ul><ul><ul><li>Ensatina escholtzii escholtzii </li></ul></ul><ul><ul><li>E. e. klauberi </li></ul></ul>
    7. 7. Species
    8. 8. The Science of Zoology <ul><li>Entomology </li></ul><ul><li>Herpetology </li></ul><ul><li>Ichthyology </li></ul><ul><li>Mammalogy </li></ul><ul><li>Ornithology </li></ul>
    9. 9. Fundamental Properties of Life <ul><li>Does Life Have Defining Properties? </li></ul><ul><ul><li>What is life? </li></ul></ul>
    10. 10. Environmental Interaction <ul><li>Ecology is the study of this interaction between organisms and between organisms and their environment. </li></ul>
    11. 11. Prokaryotic vs. Eukaryotic Cells
    12. 12. Components of Eukaryotic Cells
    13. 13. Cytoskeleton <ul><li>Microtubules </li></ul><ul><ul><li>tubulin . </li></ul></ul>
    14. 14. Biological Hierarchy
    15. 15. Evolution and Heredity <ul><ul><li>Darwin’s Theory of Evolution </li></ul></ul><ul><ul><li>The Chromosomal Theory of Inheritance </li></ul></ul>
    16. 16. Mendelian Heredity <ul><li>Gregor Mendel performed experiments on garden peas leading to an understanding of how chromosomal inheritance works. </li></ul>
    17. 17. Mendel’s Peas
    18. 18. Darwin’s Revolutionary Theory
    19. 19. Pre-Darwinian Evolutionary Ideas <ul><li>Jean Lamarck </li></ul>Empedocles Aristotle
    20. 20. Uniformitarianism <ul><li>Charles Lyell’s Principles of Geology </li></ul>
    21. 21. The Voyage of the Beagle
    22. 22. The Voyage of the Beagle
    23. 23. Alfred Russell Wallace
    24. 24. After the Voyage
    25. 25. Theory of Evolution
    26. 26. Natural Selection
    27. 27. Artificial Selection
    28. 28. Fossils
    29. 29. The Fossil Record
    30. 30. Homologous structures
    31. 31. Vestigial Organs
    32. 32. Unity in Diversity <ul><li>All mammalian forelimbs share an underlying structure utilizing the same parts, but have evolved a diverse array of adaptations, as seen in the wing of a bat, the flipper of a whale, & a human arm. </li></ul>
    33. 33. Sorting Homology from Analogy
    34. 34. Phylogeny <ul><li>cladogram </li></ul>
    35. 35. Phylogeny
    36. 36. Tree of Life
    37. 37. Populations Genetics A prime example of an exuberant polymorphism is the Hawaiian Happy-face Spider, which has been studied by Dr Geoff Oxford and colleagues. (Photo Credit: Image courtesy of University of York)
    38. 38. Populations
    39. 39. Where Does Variation Come From? <ul><li>Two processes provide the variation in gene pools. </li></ul><ul><ul><li>Mutation </li></ul></ul><ul><ul><li>Sexual recombination </li></ul></ul>
    40. 40. Gene Mutations
    41. 41. Sexual Recombination
    42. 42. Genetic Drift
    43. 43. The Bottleneck Effect
    44. 44. The Bottleneck Effect
    45. 45. The Founder Effect
    46. 46. Gene Flow
    47. 47. Modes of Selection <ul><li>Stabilizing </li></ul><ul><li>Directional </li></ul><ul><li>Disruptive </li></ul>
    48. 48. Genetic Variation
    49. 49. Polymorphism
    50. 50. Allopatric Speciation
    51. 51. Parapatric Speciation
    52. 52. Sympatric Speciation
    53. 53. Ecological Niche <ul><li>Habitat </li></ul><ul><li>Ecological Niche </li></ul><ul><ul><li>Generalists - Broad niche </li></ul></ul><ul><ul><li>Specialists - Narrow niche </li></ul></ul>
    54. 54. Resource Partitioning <ul><li>Law of Competitive Exclusion </li></ul>
    55. 55. <ul><li>resource partitioning </li></ul><ul><li>radiative evolution </li></ul>
    56. 56. Levels of Organization Levels increase in complexity as the numbers and interactions between organisms increase.
    57. 57. Energy in an Ecosystem <ul><li>Autotrophs </li></ul><ul><li>Heterotrophs </li></ul>A lynx is a heterotroph.
    58. 58. SPECIES INTERACTIONS <ul><li>predator – prey </li></ul><ul><ul><li>Co-evolution </li></ul></ul>
    59. 59. Competition <ul><li>Interspecific </li></ul><ul><li>Intraspecific </li></ul><ul><ul><ul><li>Territoriality </li></ul></ul></ul>
    60. 60. Symbiosis <ul><li>Symbiosis </li></ul><ul><ul><li>Commensalism </li></ul></ul><ul><ul><li>Mutualism </li></ul></ul><ul><ul><li>Parasitism </li></ul></ul>
    61. 61. Symbiotic Relationships <ul><li>Mutualism </li></ul><ul><li>Commensalism </li></ul><ul><li>Parasitism </li></ul>
    62. 62. That’s All Folks
    63. 63. Major Divisions of Life <ul><li>Aristotle’s two kingdom system included plants and animals. </li></ul><ul><ul><li>One-celled organisms became a problem </li></ul></ul><ul><li>Haeckel (1866) proposed Protista for single-celled organisms. </li></ul><ul><li>R.H. Whittaker (1969) proposed a five-kingdom system to distinguish prokaryotes and fungi. </li></ul>
    64. 64. Major Divisions of Life
    65. 65. Major Division of Life <ul><li>More revisions are necessary to clarify taxonomic kingdoms based on monophyly. </li></ul><ul><li>“ Protozoa” </li></ul><ul><ul><li>Neither animals nor a valid monophyletic taxon. </li></ul></ul><ul><li>“ Protista” </li></ul><ul><ul><li>Not a monophyletic kingdom. </li></ul></ul><ul><ul><li>Most likely composed of seven or more phyla. </li></ul></ul>
    66. 66. Major Subdivisions of the Animal Kingdom <ul><li>Traditional groupings based on embryological and anatomical characters: </li></ul><ul><li>Branch A ( Mesozoa ): phylum Mesozoa, the mesozoa </li></ul><ul><li>Branch B ( Parazoa ): phylum Porifera, the sponges and phylum Placozoa </li></ul><ul><li>Branch C ( Eumetazoa ): all other phyla </li></ul>
    67. 68. Sexual Selection <ul><li>Sexual dimorphism </li></ul>
    68. 69. Intrasexual Selection
    69. 70. Intersexual Selection
    70. 71. Reproduction
    71. 72. Asexual Reproduction
    72. 73. Asexual Reproduction
    73. 74. Asexual Reproduction - Advantages
    74. 75. Sexual Reproduction
    75. 76. Parthenogenesis <ul><li>Parthenogenesis involves the development of an embryo from an unfertilized egg or one where sperm & egg nuclei did not fuse. </li></ul><ul><ul><li>Ameiotic parthenogenesis – no meiosis, egg is formed by mitosis (diploid) </li></ul></ul><ul><ul><li>Meiotic parthenogenesis – haploid ovum formed by meiosis, it may be activated by a male (or not). </li></ul></ul>
    76. 77. Parthenogenesis <ul><li>In some animals (aphids, rotifers, Daphnia ) the females can produce two types of eggs. </li></ul><ul><ul><li>One must be fertilized. </li></ul></ul><ul><ul><li>One type will develop directly into haploid adults – parthenogenesis . </li></ul></ul><ul><ul><ul><li>Haploid females produce eggs by mitosis. </li></ul></ul></ul>
    77. 78. Parthenogenesis <ul><li>Daphnia reproduce asexually (parthenogenesis) when conditions are favorable. </li></ul><ul><li>In times of environmental stress, they utilize sexual reproduction. </li></ul><ul><ul><li>Increases variation! </li></ul></ul>
    78. 79. Parthenogenesis <ul><li>In many social insects, like honeybees, males (drones) are haploid and are produced by parthenogenesis while females (workers & queens) develop from fertilized eggs. </li></ul>
    79. 80. Parthenogenesis <ul><li>Parthenogenesis occurs in vertebrates in some fishes, amphibians, and lizards. </li></ul><ul><ul><li>After meiosis, the chromosomes are doubled, creating diploid “zygotes”. </li></ul></ul><ul><ul><li>Often mating behavior is required to stimulate development of offspring. </li></ul></ul>
    80. 81. Hermaphroditism <ul><li>Hermaphroditism occurs when an organism has both male and female reproductive systems. </li></ul><ul><ul><li>Monoecious </li></ul></ul><ul><ul><li>Some can fertilize themselves. </li></ul></ul><ul><ul><li>Usually a mate is required – they can fertilize each other. </li></ul></ul>
    81. 82. Sequential Hermaphroditism <ul><li>In sequential hermaphroditism , an individual reverses its sex during its lifetime. </li></ul><ul><ul><li>In wrasses, sex reversal is associated with age, size and social conditions. </li></ul></ul><ul><ul><li>Fish are female first. </li></ul></ul><ul><ul><li>The largest female becomes male if the previous male dies. </li></ul></ul>
    82. 83. Sequential Hermaphroditism <ul><li>There are also sequential hermaphrodites that are male first, later changing to female. </li></ul><ul><li>This occurs in species that produce more eggs at a bigger size – so it is advantageous to have larger females. </li></ul><ul><ul><li>Oysters </li></ul></ul>
    83. 84. Fertilization <ul><li>Fertilization – fusion of egg and sperm into a single diploid cell, the zygote . </li></ul><ul><ul><li>External </li></ul></ul><ul><ul><li>Internal </li></ul></ul>
    84. 85. External Fertilization <ul><li>External fertilization – fertilization takes place outside the female’s body. </li></ul><ul><ul><li>A wet environment is required so gametes don’t dry out and so sperm may swim to the eggs. </li></ul></ul>
    85. 86. External Fertilization <ul><li>Environmental cues (day length, temperature) or chemical cues may cause a whole population to release gametes at once. </li></ul><ul><ul><li>Increases likelihood of fertilization. </li></ul></ul>© 1999 New World Publications.
    86. 87. Internal Fertilization <ul><li>Internal fertilization allows terrestrial animals to reproduce away from water. </li></ul><ul><ul><li>Cooperative behavior leading to copulation is required. </li></ul></ul>
    87. 88. Ensuring Survival of Offspring <ul><li>Species with external fertilization produce huge quantities of gametes that result in lots of zygotes. </li></ul><ul><ul><li>Predation on young is high. </li></ul></ul><ul><ul><li>Few will survive to reproduce. </li></ul></ul>
    88. 89. Ensuring Survival of Offspring <ul><li>Species with internal fertilization produce fewer zygotes, but protect them more from predation. </li></ul><ul><ul><li>Tough eggshells </li></ul></ul><ul><ul><li>Embryo may develop in reproductive tract of female </li></ul></ul><ul><ul><li>Parental care of eggs & offspring </li></ul></ul>
    89. 90. Advantages of Sexual Reproduction <ul><li>Sexual reproduction has costs including finding mates, greater energy cost, reduced proportion of genes passed on to offspring, and slower population growth. </li></ul><ul><li>However, sexual reproduction increases variability in the population – important during times of environmental change. </li></ul>
    90. 91. Gamete Production & Delivery <ul><li>Gametes (eggs & sperm) are required for sexual reproduction. </li></ul><ul><li>Usually, gametes are produced in gonads (ovaries & testes). </li></ul><ul><li>Germ cells are set aside early in development. They will produce only gametes. </li></ul>
    91. 92. Reproductive Patterns <ul><li>Oviparous – animals that lay eggs. </li></ul><ul><ul><li>Most invertebrates, many vertebrates </li></ul></ul><ul><li>Ovoviviparous – animals that retain the eggs within their bodies. Nourishment comes from the egg. </li></ul><ul><ul><li>Some annelids, insects, some fishes, reptiles. </li></ul></ul><ul><li>Viviparous – eggs develop in oviduct or uterus, nourishment from mother. </li></ul><ul><ul><li>Mammals, some sharks, scorpions. </li></ul></ul>
    92. 93. Invertebrate Reproductive Systems <ul><li>Many insects have separate sexes, internal fertilization and have complex reproductive systems. </li></ul><ul><ul><li>Female crickets use long ovipositors to deposit eggs. </li></ul></ul>