BIS 2B: Introduction to Biology - Ecology and Evolution - Biology

BIS 2B: Introduction to Biology - Ecology and Evolution - Biology

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BIS 2B is part of the UC Davis Biological Sciences lower division core sequence and is designed to provide a foundation for study of modern biology for a broad range of majors. BIS 2B explores the ecological and evolutionary processes that shape biological diversity and acquaints you with the physical challenges of the environment. This course complements how BIS 2A treats the fundamental molecular, cellular, developmental, physiological, and genetic building blocks of living organisms, and the origins of life itself and how BIS 2C considers the diversity of life on earth that is the outcome of several billion years of continuous evolution and ecology.

Specifically, this course covers the processes by which organisms have evolved over the 3.5+ billion years of the existence of life on Earth (evolution) and the present-day processes by which those species interact with each other and the environment to create the habitats, patterns of distribution and abundance of species we see around us (ecology). As you will certainly see throughout the quarter, evolution and ecology are fundamentally linked: evolutionary history shapes a species’ ecology, and present-day ecology can influence future evolutionary trajectories. This is why they are studied together in this course,

Ecology, Behavior and Evolution

The Ecology, Behavior, and Evolution major includes the fields of population biology, ecology, conservation biology, animal behavior, population genetics, biogeography, and evolution. These fields have in common a focus on evolutionary processes and whole organisms in relation to each other and to their environments. Because organismal biology spans such a wide variety of topics, this major has been designed to provide the basic fundamentals while allowing maximum flexibility within the general topic areas. Research careers in ecology, behavior, and evolution can be found in universities, government agencies, and the biotechnology industry. More applied careers are equally varied: recent graduates now work in forestry and wildlife management, as ecological consultants for US and foreign governments and private industry, as teachers, or in new fields such as ecological medicine and epidemiology, environmental design and planning, restoration ecology and conservation biology.

The major requirements below ONLY apply to students who were admitted to UC San Diego in Fall 2018. 

BIS 2B Lecture 21

Competitive character displacement - Interspecific competition can have major effect on the fitness of organisms - Shape evolution of traits of organisms that they express - Idea of competitive character displacement is that natural selection will favor traits that reduce the intensity of competition - Whole variety of traits that are associated with the specific resources that are being used - morphological/behavioral/physiological traits can evolve under interspecific

  • Look at the zone of overlap, you see they may start to use somewhat different resources, greater divergence
  • Also look fitness functions, by plotting trait that organism expresses vs fitness, organism may have higher fitness when using traits that are more different than resources that competitor is using Example:
  • Two species of spadefoot toads
  • Spea multiplicata
  • Spea bombifrons
  • Both may converge somewhere, at tadpole stage can eat two general classes of food
  • Detritus- decaying organic material, easy food to find/ingest, but very hard to digest/low quality
  • Fairy shrimp- hard food to find/ingest, but very easy to digest/high quality/high protein
  • Both toads exhibit morphologies by genes.
  • Tadpoles that eat the detritus develop a more detritivore morphology: small jaws, smooth mouthparts, long gut
  • Tadpoles that eat the fair shrimp develop a more carnivorous morphology: large jaws, serrated mouthparts, short gut
  • Morphology that is expressed is partly due to genes, and what they eat when they

are developing: phenotypic plasticity

  • Look at two species when they live separately (NO interspecific)
  • Don't look at fitness, look proxy fitness that is closely associated with fitness
  • This is size of tadpole, bigger it gets = high probability of survival
  • More likely to reach adult stage, bigger tadpoles make bigger adults, bigger adults, bigger males will fuck more, bigger females make more eggs


- The U-shape would describe the fitness function as disruptive selection: individuals whose phenotype is farther away from the mean, the ones that are favored by natural selection - Meaning its phenotype needs to have really sharp teeth and all attributes as carnivore to survive OR need have attributes of detritivore to survive HIGH FITNESS - The mean phenotype will not be good for the phenotype, low fitness - Look at frequency distributions, bottom two graphs: bimodal distribution - Low fitness types that are the mean phenotypes/morphology are not very common in population - Most tadpoles will specialize in eating detritus or fairy shrimp, not really eating both - Both species eating same thing, and within species specializing eating by becoming one morph or the other under disruptive selection

  • Include herbivores eating plants, carnivores, omnivores
  • Prey may be killed, eat part of plant but not kill, parasite may not kill the host

R- intrinsic rate of increase broken down into dis (b-d+i-e)

Influence on predation on all demographic parameters

Influence of predation on b

  • Lots of alfalfa fields will find pea aphids(green bugs), attacked by Nabis
  • +Nabis: 57% reduction in pea aphid population size
    • Long beak, sharp mouthparts, try to stab aphids with beak, inject toxins and fuck it, not smooth and are clumsy
    • Only kill like 10% of aphids, other 90% flee, evolved to jump well
    • The reduction actually comes from aphid ability to jump and flee from Nabis may cost fitness functions of aphids
    • Guy bought Nabis and cut off harmful beak to aphids and they cannot kill aphids anymore but can still scare aphids shitless
    • Not because of nabis killing aphids
    • Why is so costly for aphids to die?
    • Aphids are feeding sap of alfalfa plant, sap is poor ass food
      • Hella sugar, little protein,
      • Pea aphids take 90% sucking sap of plants, always sucking
      • Takes one hour, if jumps off, to resettle find new location to feed again
      • No way to compensate for lost feeding time
      • Every jump, lose 10% of reproductive capacity

      Influence on predation on e

      • Aphis gossypii
        • 25% winged offspring, no predators
        • 63% winged offspring, had predators
        • They detected predators that left these chemicals that can harm and above gave the percentage that developed wings and the ones that didn’t
        • Influence on predation on i
        • Mosquitoes- live in temporary bodies of waters
        • Mothers making eggs controlling rate of immigration to particular patch of habitat
        • Prescence of predators influencing immigration, put two tubs of water one that has and does not have predators, not good idea?
        • Count ones that leave or the ones that get eaten
        • Cant determine immigrayion from mortaility
        • Do predators control rate of immigration
        • Do this way
        • Both buckets of water do not have predators but one is clean, but other that had the predator bucket has scent of death
        • Mosquito (Culiseta), reduced egg-laying by 91% in the bucket of death
        • Can detect odor asscociated with predator, even when predator is not present, even before they land

        Study questions Lecture 21, Competitive character displacement Predation

        Watch the video: Key Ecology Terms. Ecology and Environment. Biology. FuseSchool (July 2022).


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