BIOLOGY 1B Lecture Notes - Lecture 2: Plecoptera, Mayfly, Caddisfly
12 Jun 2018
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Lecture 2
• Three definitions of ecology:
o The study of the relationships between organisms and their environment
o The study of the distribution and abundance of organisms
o The study of the transformation and flux of matter and energy in natural systems
• Species distribution: distributions are patchy at multiple scales
o Causes of distribution limits may be different at different scales and in different parts of
the range
o Why is this species not found everywhere within its range?
o Dispersal: the movement of individuals or gametes away from their parent location
▪ Generational movement
▪ Could expand geographic range of population or species
o Dispersal limitation: inability to disperse; not enough time
▪ Ex. cattle egrets arrived in the Americas in late 1800s and spread over time
illustrating dispersal potential
▪ Species introductions provide unintentional transplant experiments
▪ Demonstrates that distributions at one point in time are NOT due to
environmental limits
▪ Time is key
• Global transportation: breakdown of dispersal limits
o Humans
o Moved seeds and organisms
• Biotic vs. Abiotic factors
o Biotic: living components of the environment
o Abiotic: non living components
o Soil- unsure which to categorize in because it has minerals and living material
o Biotic factors limit distribution
▪ Grazing animals eating shrubs on one side of fence and not the other
▪ Predation, parasitism, competition, disease
• Organisms shape their environment
o Every interaction between organisms changes environment
o Trees create shade
• Aquatic invertebrates and water quality
o Organisms have different tolerances to different environments
• Environmental gradient and how it helps us understand species distribution
o Environmental gradient= Continuous range of environment conditions
▪ Ex. low to high temp, low to high soil nutrient
▪ Some gradients are physically continuous (the gradient in temp moving from
bottom to top of mountain) and some are patchy in nautral world
• How three major invertebrate groups are distributed along gradients of water quality reflecting
differences in their environmental tolerance
• Distributions are usually unimodal
o Do best in one kind of environment
• 3 major invertebrate groups: related species don’t diverge that much usually
o Ephemeroptera
o Trichoptera
o Plecoptera
o Tolerance more high quality water
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