comparative vertebrate biology

• Define selection and explain how it differs from random processes in evolution.

  Selection is the non-random differential survival or reproduction of organisms based on traits that improve fitness. Unlike random processes like genetic drift, selection consistently favours traits that increase survival or reproductive success.
• Compare and contrast 3 types of natural selection: directional, disruptive, and stabilising. Provide an example of each.

  Directional selection - Favours one extreme trait (eg. faster cheetahs).

  Disruptive selection - Favours both extremes, creating bimodal distribution (eg. small and large beak sizes in Darwin's finches).

  Stabilising selection - Favours intermediate traits (eg. human birth weights).
• What is artificial selection, and how does it differ from natural selection?

  Artificial selection is when humans choose specific traits to generate in a population (eg. breeding crops or dogs). It differs from natural selection as fitness is determined by human preference, not environmental pressures.
• Debate whether sexual selection is a component of natural selection or a separate process.

  Sexual selection is a subset of natural selection focused on reproductive success rather than survival.
• What is sexual conflict, and how does it lead to sexual selection?

  Sexual conflict arises from differing reproductive interests between males and females, driving traits and behaviours that enhance reproductive success in one sex, even at a cost to the other.
• Differentiate between intrasexual selection and intersexual selection, providing an example of each.

  Intrasexual selection - Competition within the same sex (eg. male-male combat in deer).

  Intersexual selection - Mate choice by one sex (eg. peahens choosing males with large tails).
• Explain the role of mate choice in sexual selection. Why is it typically stronger in one sex?

  Mate choice is stronger in females because they typically invest more in offspring (eg. eggs, pregnancy, parental care), making them selective about mates with desirable traits.
• Match the traits to mechanisms:

  A stag's large antlers? Same-sex contests

  The bright plumage of a male peacock? Mate preferences

  Mate guarding behaviour? Sperm competition

  A male's ability to detect females earlier in the breeding season? Scramble competition

  Increased testes size in primates? Sperm competition
• Mechanisms of sexual selection.

  Same-sex contests - Traits that improve success in competition.

  Scramble competition - Sensory and movement traits to locate mates more effectively.

  Endurance rivalry - Reproductive success by outlasting competitors during mating seasons.

  Sperm competition - Traits related to sperm abundance, displacement, and mate guarding.

  Mate preferences - Preferences for traits not directly linked to survival, such as attractiveness and fecundity.
• Discuss the role of coercion and infanticide in sexual selection.

  Coercion - Increases male mating success but may harm females by reducing their fitness.

  Infanticide - Males kill offspring to bring females back into estrus, maximising their own reproductive opportunities.
• Define sexual dimorphism and explain how it arises.

  Sexual dimorphism is the physical difference between sexes (eg. size or colouration). It arises through mechanisms like same-sex contests and mate preferences, where traits in one sex are selected to enhance reproductive success.
• What are alternative mating strategies? Provide an example.

  Alternative mating strategies are behaviours or traits that differ from the norm but still enhance reproductive success (eg. sneaker males in fish who mimic females to gain access to mates).
• How might sexual selection influence human evolution?

  Sexual selection could explain traits like facial symmetry, secondary sexual characteristics (eg. voice pitch, body shape), and behaviours that increase attractiveness or reproductive success.
• When might sexual selection conflict with natural selection?

  When traits that increase mating success (eg. loud calls) also increase predation risk. This conflict can be resolved if the reproductive advantage outweighs survival costs.
• What is biomechanics?


  The study of animal movement and how animals navigate / adapt to their surroundings.
• What does studying extinct animals give insight too?

  The forms not found in present day so you can understand physical limits of animals.
• Skeletal adaptations to size

  • Small animals do not scale-up proportionally.
  • Thinner bones and crouched position
  • Larger animals
  • Thicker, robust bones and a straight column-like posture
• What is quadrupedalism?

  The movement on all four limbs.

  • Seen in most tetrapods and offers stability.
• What is bipedalism?

  The movement on two hind-limbs.

  • Obligate bipedalism in birds and humans.
  • Obligate bipeds have erect postures.
  • Obligate bipedalism enabled new innovations such as flight in dinosaurs (birds) and increased manual dexterity.
• Adaptations to speed and size:

  • Cursorial - Distal limbs longer than proximal.
  • Adaptation to increase running efficiency and speed.
  • Graviportal - Proximal limbs are longer and more robust.
  • Adaptation to support large body size.
• What do the following words mean?

  • Plantigrade - Entire foot on ground (eg. human)
  • Digitigrade - Ankle or wrist elevated (eg. dog, cat, bird)
  • Unguligrade - Tips of digits on ground (eg. horse, cows)
• There are multiple strategies to increase stride and speed without changing limb length or posture:

  • Lateral (side to side) spine movement.
  • Sagittal (up and down) spine movement.
  • Pelvic (hip) rotation during movement.
• What is life history?

  Life history refers to the pattern of survival and reproduction events during the life of an organism.
• What are some of the key life history traits?

  • Age at first reproduction
  • adult body size
  • number of offspring
  • size of offspring
  • reproductive lifespan
  • number of reproductive events
  • mortality rate
  • body size
  • growth rate
  • post-reproductive investment (eg. parental care)
• Huge variability in key traits

  • Reproductive age varies across species, often correlating with lifespan and survival rates.
  • Litter size and investment - Influences parental investment.
  • Limited resources means parents will either invest heavily in fewer (quality) or spread investment equally (quantity).
  • Parental care evolution likely evolved when the benefits of increased offspring survival outweighed the cost to parents future survival or reproduction.
• What is the Darwinian Demon concept:

  A hypothetical organism perfectly adapted to maximise survival and reproduction, free of biological constraints.

  • In reality, resources are limited, leading to trade-offs between life history traits, preventing such 'demons' from existing.
• What is an iteroparous species?

  A species that reproduces multiple times over their lifetime (eg. most vertebrates).

  There are 2 types:

  • Seasonal
  • Continuous
• What is a semelparous species?

  A species that reproduces once and then dies, investing heavily in this single reproductive event.

  (eg. beetles and salmon)
• Classic life history strategies:

  • R-strategies - Emphasise quantity of offspring. It is suited for unstable environments (eg. mice, frogs and insects).
  • K-strategies - Emphasise quality and survival of fewer offspring. It is suited for stable environments (eg. elephants, humans and whales).
• What do mating systems depend on?

  Spatial distribution of resources and life history strategies
• What is polygamy?

  When an individual mates with multiple others
• What is harem polygyny?

  A single male mates with multiple females
• How does sequential polygyny differ from harem polygyny?

  Sequential polygyny involves short-term pair bonds
• What is scramble polygyny?

  Male tries to mate with as many females as possible
• What defines monogamy?

  One male and one female form an exclusive bond
• What is polyandry?

  One female mates with multiple males
• Why is genetic diversity important in mating systems?

  It enhances the adaptability and survival of species
• What are fitness gains in the context of mating systems?

  Benefits that improve reproductive success
• What is cryptic female choice?

  Females influence mating success after copulation
• What is promiscuity in mating systems?

  Both male and female mate randomly with multiple partners