Evolution of Vertebrates
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Questions and Answers

What percentage of all known species are still in existence?

  • Fewer than 1% (correct)
  • About 25%
  • About 10%
  • More than 50%

    • What is exaptation?

  • The evolution of a trait to serve a different function (correct)
  • The development of a new gene
  • The formation of a new chromosome
  • The evolution of a new species

    • What is the main difference between homologous and analogous structures?

  • Their size and shape
  • Their color and texture
  • Their location and type
  • Their function and origin (correct)

    • What is the average weight of a human brain?

    <p>1000-2000 grams</p> Signup and view all the answers

    Why do humans generally form monogamous bonds?

    <p>Because of evolutionary theory</p> Signup and view all the answers

    What type of trait is eye color?

    <p>Dichotomous</p> Signup and view all the answers

    What is the purpose of meiosis?

    <p>To produce gametes</p> Signup and view all the answers

    What is the result of genetic recombination during meiosis?

    <p>Unique, spliced together recombinations of chromosomes</p> Signup and view all the answers

    What is the next stage after meiosis?

    <p>Mitosis</p> Signup and view all the answers

    How many pairs of chromosomes do humans have?

    <p>23 pairs</p> Signup and view all the answers

    What adaptation allowed reptiles to reduce their reliance on watery habitats?

    <p>Developing dry scales</p> Signup and view all the answers

    What is unique about the way mammals nurture their young?

    <p>Females feed their young with secretions of mammary glands</p> Signup and view all the answers

    What is the estimated time when the first Homo species emerged from Australopithecus?

    <p>4 million years ago</p> Signup and view all the answers

    What is characteristic of apes?

    <p>They can walk upright for short distances and have long arms</p> Signup and view all the answers

    What is the approximate height of Australopithecus?

    <p>1.3 meters</p> Signup and view all the answers

    What is the class of mammals that humans belong to?

    <p>Mammal</p> Signup and view all the answers

    What is the name of the order that humans belong to?

    <p>Primate</p> Signup and view all the answers

    What is the name of the genus that humans belong to?

    <p>Homo</p> Signup and view all the answers

    What was the first group of organisms to evolve 250 million years after the appearance of complex multicellular water-dwelling organisms on earth?

    <p>Chordates</p> Signup and view all the answers

    What is the main function of the spinal bone in vertebrates?

    <p>To protect the dorsal nerve cords</p> Signup and view all the answers

    What was the first group of vertebrates to evolve?

    <p>Primitive bony fishes</p> Signup and view all the answers

    Why did bony fishes venture out of the water 410 million years ago?

    <p>To escape stagnant pools and take advantage of terrestrial food sources</p> Signup and view all the answers

    What was the result of the transformation of fins and gills of bony fishes through natural selection?

    <p>The evolution of amphibians</p> Signup and view all the answers

    What is a characteristic of amphibians in their larval form?

    <p>They must live in water</p> Signup and view all the answers

    Study Notes

    Evolution of Vertebrates

    • Complex multicellular water-dwelling organisms first appeared on earth about 800 million years ago
    • 250 million years later, chordates (animals with dorsal nerve cords) evolved
    • First chordates with spinal bones (vertebrae) to protect the dorsal nerve cords evolved 25 million years later
    • First vertebrates were primitive bony fishes, now there are 7 classes of vertebrates: 3 classes of fish, amphibians, reptiles, birds, and mammals

    Evolution of Amphibians

    • 410 million years ago, bony fishes started to venture out of the water, gaining two advantages: escaping stagnant pools and accessing terrestrial food sources
    • Through natural selection, fins and gills of bony fishes transformed into legs and lungs, giving rise to the first amphibians 370 million years ago
    • Amphibians in larval form must live in water, while only adults can survive on land

    Evolution of Reptiles

    • 315 million years ago, reptiles evolved from a branch of amphibians, laying shell-covered eggs and covered by dry scales
    • These adaptations reduced the reliance of reptiles on watery habitats
    • Reptiles spend their first stage of life in watery habitats, then live far from water due to dry scales reducing water loss through their water-permeable skin

    Evolution of Mammals

    • 225 million years ago, a new class of vertebrates evolved from a small reptile line, characterized by females feeding their young with mammary gland secretions
    • Females nurture their young in a watery environment within their bodies until they are mature enough to be born
    • There are 26 different orders of mammals, including primates, with 16 groups of primates, such as apes and old world monkeys

    Emergence of Humankind

    • Humans are known as hominins, including 6 subgroups, such as Australopithecus and Homo
    • Homo is thought to be composed of at least eight species, seven of which are now extinct
    • The first Homo species emerged from Australopithecus 4 million years ago, while Homo sapiens emerged 275,000 years ago
    • Australopithecus were about 1.3 meters tall, with small brains and pelvic and leg bones indicating they were upright
    • Distinctive features of Homo include larger brain cavities than Australopithecus but smaller than modern humans

    Classification of Humans

    • Kingdom: animals
    • Phylum: chordate
    • Class: mammal
    • Order: primate
    • Family: Hominid
    • Tribe: Hominin
    • Genus: Homo
    • Species: sapiens

    Thinking About Human Evolution

    • Evolution does not proceed in a single line
    • Humans have little reason to claim evolutionary supremacy, given our brief existence
    • Evolution does not always proceed slowly, and rapid changes can be triggered by sudden environmental changes
    • Fewer than 1% of all known species are still in existence
    • Evolution does not progress to preordained perfection
    • Not all existing behaviors or structures are adaptive, and some may be incidental by-products (spandrels)
    • Not all existing adaptive characteristics evolved to perform their current function
    • Exaptation: evolved to serve one function, later co-opted to serve another
    • Homologous: structures similar among species
    • Analogous: structures similar but with different evolutionary origins
    • Convergent: evolution of different species using the same solution as demanded by the environment

    Evolution of Human Brain

    • There is no clear relationship between overall brain size and intelligence
    • Brain size (cerebrum) increased during evolution
    • Increase in number of convolutions (folds on cerebral surface) greatly increased the surface area of the cerebral cortex

    Understanding Mate Bonding

    • Most mate bonds are promiscuous
    • Most mammals form polygynous mating bonds
    • Polyandry: males contribute to reproduction more than females
    • Humans generally form monogamous bonds (one on one)
    • Mate bonding in humans is predicted through evolutionary theory
    • Men value youth and attractiveness in partners
    • Women value power and earning capacity in partners
    • Physically attractive women bond with men with high status
    • Mate attraction: F = physical attraction, M = display power and resources
    • Men are more likely than women to commit adultery

    Fundamental Genetics

    Mendelian Genetics

    • Dichotomous traits: occur in one form or another, never in combination
    • True breeding lines: breeding lines where interbred members always produce offspring with the same trait generation after generation
    • Dominant trait: appears in all first-generation offspring
    • Recessive trait: appears in about one quarter of the second-generation offspring
    • Phenotype: an organism's observable trait
    • Genotype: traits passed on through genetic material
    • Homozygous: identical alleles (BB)
    • Heterozygous: different alleles (Bw)

    Chromosomes

    • Genes are in chromosomes
    • Humans have 23 pairs of chromosomes with an allele on each chromosome
    • Meiosis (producing gametes): chromosomes divide and one of each pair goes to each of the two gametes that result from cell division
    • First stage, chromosomes line up in pairs
    • Then crossover occurs, forming a linkage, and break apart to exchange sections
    • As a result of genetic recombination, each of the gametes that formed zygotes contains chromosomes that are unique, spliced together recombinations of chromosomes from parents
    • After meiosis, mitosis occurs

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    Description

    Learn about the evolution of vertebrates, from the first complex multicellular water dwelling organisms to the development of chordates and spinal bones. Understand the timeline of human evolution and the characteristics of vertebrates.

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