Bio Notes

C1.4 - Speciation

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C1.4 - Speciation

What is a species?

  • species: members of a population that can interbreed and produce viable offspring
    • known as the biological species concept
    • limitation: does not include asexually reproductive species or fossils
  • Reproductively isolated
  • No gene flow through different species
  • Species differentiated by appearance or morphology
  • morphology: change in form
  • genus: a “clan name” for living things, what group a species belongs to

Taxonomy of Life

In order: domain, kingdom, phylum, class, order, family, genus, species

Taxonomy of Life diagram

Binomial Nomenclature of Life

  • Designed by Carolus Linnaeus [Latinized name] (1707-78), Swedish botanist
  • botanist: person who studies plants
  • binomial nomenclature: naming system (of life) involving two names
  • THE NAMING SYSTEM
    • Genus species
    • i.e. Homo sapien
  • Puts species w/ most similarities closest together
  • Linnaeus’s first book had 12 pages
  • 12th ed: 1,500 pages

Speciation + Hybrids

  • speciation: evolutionary formation of new species
  • microevolution: evolutionary changes that occur within a species
  • macroevolution: evolutionary changes taht result in a new species formation
  • hybrid: offspring that results from mating of individuals from two different species

Reproductive Isolating Mechanisms

  • Speciation is a result of reproductive isolation
  • Prevents individuals from different (or same, but separated) species from mating together
  • Prezygotic mechanisms prevent fertilization
  • Postzygotic mechanisms prevent zygote from becoming a healthy or fertile adult
  • zygote: the individual that forms when sperm cell meets egg cell
  • fertility: ability to produce healthy offspring

Ecological / Geographic Isolation

  • ecological / geographic isolation: species occupying seperate habitats or niches
  • Usually seperated by dramatic barriers to travel
  • Species do not encounter one another and can’t mate together
    • i.e. rodent populations at diff. altitudes, or species seperated by mountain range

New Guinea topology, central red line is the mountain range, New Guinea Highlands

New Guinea topology

Speciation diagram

Speciation diagram, geographic isolation

Habitat Isolation

  • habitat isolation: similar species reproductively isolated due to adapting to habitats in the same general location
  • Examples
    • 2 species of three-spined stickleback fish in B.C. lakes: one lives off of snails at seafloor whereas others feed off plankton near the surface
    • 2 species of garter snake: one lives on land, other lives on water
    • 2 species of oak tree: one grows in sandy soil, but other grows in loamy soil

Temporal Isolation

  • temporal isolation: isolation that occurs when reproductive cycles occur at different times
  • Reproductive cycles occur at different times
  • Species overlap geographically but flowering time or mating seasons do not
    • i.e. certain cacti flower at night, others at daytime

Mechanical Isolation

  • mechanical isolation: isolation from structural / physical incompatibilities of reproductive or sexual organs
  • Structural differences in reproductive organs
  • arthropod: phlyum of invertabrates w/ jointed exoskeletons
    • includes insects, crustaceans, arachnids
  • Arthropod penis shape prevents mating between closely related species
  • Orchids are adapted to specific pollinators, preventing species cross-pollination

Other Forms of Isolation

  • behavioural isolation: isolation when species have different relationship or mating behaviours
    • i.e. Eastern and western meadowhawks are seperate species because they have different relationship rituals, including songs to attract mates
  • gametic isolation: isolation when sperm and eggs of different species are unable to recognize / incompatible with each other
  • hybrid inviability: hybrid produced is unhealthy, underdeveloped, and/or weak
  • hybrid infertility: hybrid produced is healthy, but cannot reproduce

Hybrids

  • hybrid: offspring of gentically dissimilar parents
  • Postzygotic isolation
  • Hybrid zygote may develop into a healthy adult
  • Offspring usually sterile
  • i.e. mule
  • In plants, hybrid vigor may result
  • hybrid vigor: when hybrid plant produces larger flowers or fruits

Effect of Human Activities

  • Humans introduced new non-native predators while exploring new places
  • Non-native predators kill off a lot of native species
  • Some species mistake human pollution for food or get stuck in human activities like fishing nets or plastic bags
  • Examples of endangered species
    • kakapo, flightless parrot, endangered due to pets and livestock, easy prey
    • leatherback turtle, get caught in fishing equipment, eat plastic bags thinking they are jellyfish, and they and eggs are hunted in breeding grounds in Central / South America

Parapatric Speciation

  • Parent species occupies a continous habitat within same geographical area
  • Population enters a new niche and becomes reproductively isolated
  • Two populations live side by side or continously
  • i.e. Two species of frogs live on wetlands and drylands. Over time, they adapt to their environment and can’t interbreed

Ring Species

  • Form of parapatric speciation
  • Connected series of neighbouring populations that can interbreed
  • However, two end populations are so different that they can’t interbreed anymore

Sources

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