Lecture 6. Life history and pop dynamics -posted

Lecture 6. Life history and pop dynamics -posted - The...

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The niche - a preliminary definition: The set of environmental conditions under which organisms can grow and reproduce (salinity, temperature, humidity, etc)
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Example: The “fundamental” niche of the 7-spine shrimp We’ll talk later about how the niche may be modified: Either expanded or contracted through interactions with other species to produce the “realized” niche
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A species’ LIFE HISTORY is how, when and where life cycle events occur 1N 2N 1N HAPLOID STAGE mating fertilization DIPLOID STAGE *dispersal? development *dispersal? survival, growth and development survival, growth and development *dispersal? Post-reproduction survival, growth and development? reproductive maturation reproductive investment *dispersal? 2N
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Indirect development : involves a larval stage and metamorphosis into adult form . Direct development : juvenile forms emerge from mother or egg in adult-like form Developmental patterns: direct versus indirect development Nymphs Adult True “bugs”
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The Principle of Allocation: there is a tradeoff between the number of offspring and investment per offspring! Example: three major dispersal “strategies” in the larvae of marine invertebrates Planktotrophic Lecithotrophic Non-pelagic Many, tiny (~100µ ) Long period of dispersal Fewer, small (<1mm) Less time in dispersal phase Fewest, large (>1mm)
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Making sense of the terminology __trophic – as a suffix, means having to do with the organism’s feeding mechanism Planktotrophic – feeds on plankton Lecithotrophic – is provisioned with all the resources it will use in its larval stage; does not feed (“lecitho” means “pertaining to the yolk of an egg”) Non-pelagic – does not disperse through the water column (pelagic environment); may receive parental care
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Other groups have tradeoffs between quantity and quality in offspring production
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Why is dispersal a good thing? Benefits of dispersal: - find new habitat when local conditions degrade - escape competition, esp. with close relatives - avoid inbreeding with close relatives - decreases chance of total lineage failure (“spreading the risk”) Costs of dispersal: - less feeding and growth - high risk of individual mortality - reduced chance of finding suitable habitat Natural selection favors dispersal “strategies” that increase Benefits - Costs
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offspring as density increases… why? Some protozoans shift to cannibalistic lifestyle at high density, …wh
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Lecture 6. Life history and pop dynamics -posted - The...

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