BIO 120 – L07(slideshow #6)
how can you predict how populations going to do with different ages?
Stable age distributionproportions of ages remain same. This is
always recognized by having younger individuals and fewer older
Population mometum- population is overloaded in juvenile, so birh
rates are controlled to drop population.
But there is a lag (momentum)
Baby boom delay in reproducion for a while and then al of a sudden,
people have a lot of kids (like a pulse)
Age pyramids- wide base for graph- high reproduction rate, but low
Fat middle in are pyramid, declining population
taking the logisitic equation and adding species to it now
basic model:lotka-volterra equation2 species competing for resources
- resources taken by one are not available for the other ( negtive
relationship) one suffer, and the other doesn’t.
4 possible outcomes of L-V competitio: both stably coesxist, secies 1
wins (species 2 becomes extinct), species 2 wins, and dpends on which
spies has what N
experiment by gause (1930s)—see slide 10!
Paramecium, some species can coexist, but sme cant
How ar competitive effects manifested in nature?
Competitive exclusio is less likely to go to competition..
Tansley experiment growth of species depends on acidic/basic soils.
Yo have to talk about environments hen you tlk about competetion
Experiment by Connell***
Predator prey models: sin curves
Prey starts higher than predator( prey pop is growin because predatore
pop is low) Evenually, predator start producing, and so prey reduces,
when prey drops, less resouces are available for predators,so predator
This cycle is continuous
T is extremely diffcult to manipulate predator prey relation in the lab
Huffaker – mites that live on oragnes, got a lot of data because he used
a complicated environment to extend cycles, ad receive more data.
The most famous cycle- hare(arctic) vs lynx (casts
Not simple predator-prey cycles
As hare pops inceases, plant pops decreases (hares eat it all).
Two birds live in the same forest, how do they both stay alive and avoid
Warblers( birds)—many similar species coexisit in the same forest.
Each species used different parts of the tree,some nested on top, some
on the sides, some near the ground. So, basically, they coexist because
they divide space, and so have lower competition.
Niche overlap: ecological similarity. See slide 23 +24 !
Shifts in graphs could be because of evolutionary responses or