BIO3021 Lecture Notes - Lecture 6: Balanus Balanus, Intermediate Disturbance Hypothesis, Marine Life
25 May 2018
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Lecture 6 – Competition, Predation and Supply Side Ecology
• All organisms lived where they were – can tolerate that
Intertidal Zone
• Physiological tolerances of different species lead to their distribution
• Cthalamus settles everywhere
o But adults only live in top zone
o Why?
o Transplant Cthalamus to lower level and exclude Balanus from half of
transplants (competes)
o Cthalamus was undercut/overgrown by Balanus
▪ Balanus competitively excludes Cthalamus
• Dies if transplanted high up shore
Subtidal Species
• Competition more severe
• Competitive exclusion:
o Important structuring force in communities
• If competition hierarchies exist, why do some species coexist in same niches?
o Early species good colonisers but poor competitors
▪ E.g. barnacles: good colonisers but bad competitors
▪ Solitary species
▪ Produce more but smaller offspring
▪ Have feeding larvae
▪ High settlement
o Late species: poor colonisers but good competitors
▪ E.g. colonial species (corals) good at competing
• Produce larger and fewer offspring
▪ Have non feeding larvae
• Colonisation competition trade off
o Mediated by life histories
o If never disturb a community – all competitiors
Intermediate Disturbance Hypothesis
• If a place was never disturbed:
o Would have low species diversity because all good competitors
• If always disturbed:
o Low diversity because all colonisers
• Intermediate level
o Some colonisers, some competitors → quite high diversity
Predation
• Predation opens up space
• Can act like disturbance
• Predation helps reset community
• 80s view of marine communities **Summarise our understanding of marine
community ecology in 1980s
o Competition
▪ Competition colonisation tradeoff
find more resources at oneclass.com
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Document Summary
Lecture 6 competition, predation and supply side ecology: all organisms lived where they were can tolerate that. Subtidal species: competition more severe, competitive exclusion, important structuring force in communities. If a place was never disturbed: would have low species diversity because all good competitors. Intermediate level: some colonisers, some competitors quite high diversity. Crab larvae: can move up estuaries by altering their vertical position in the water column. Dispersal: whale falls and hot vents, worms live in bones of whale when dies, highly reducing chemical reaction haemoglobin (red glow) to get oxygen from water to feed bacteria break down whale fat to get energy. Vestimentiferans: tube worms that live on hydrothermal vents, red use haemoglobin to capture oxygen to feed bacteria. Use hydrosulphide to drive cycle to create sugars: independent from energy from sun. Individuals are making more eggs but fewer are becoming larvae. Exam questions: compare and contrast the relative roles of different ecological process in.
