Topic 4 Ecology

• 4.1 Species, communities and ecosystems • 4.2 Energy flow • 4.3 Carbon cycling • 4.4 Climate change

parts of an ecosystem

ecosystem > community > population > species

biotic and abiotic factors

food chains

autotrophs (self feeding) are eaten by heterotrophs in different trophic levels. mixotrophs both feed themselves and eat others

mutualism

benefit x benefit

commensialism

benefit x unaffected

parasitism

benefit x harmed

detritivores

type of heterotroph that eats non living organic sources, internal digestion, have mouths

saprotrophs

absorbs non living organic sources, external digestion using enzymes

chi squared test for association

1. define null hypothesis (no correlation) and alternative hypothesis (correlation)
2. complete contingency table (present x present, present x absent, absent x present, absent x absent, totals)
3. complete table of expected values: \[row total x column total\] / grand total
4. calculate chi squared value: \[(observed - expected)^2\] / expected → for each box. add up chi squared for each box to get final chi squared value.
5. degrees of freedom: (no. of rows - 1) x (no. of columns - 1) = this determines after how many values it becomes a sure pattern
6. match the ideal degree of freedom with 95% accuracy on a critical values table. if the previous chi squared value is bigger than the listed table value, you can be 95% sure there is a correlation.

Ecological pyramid

displays the amount of energy that gets transferred between various trophic levels \~10%

pool (reservoir)

reserve of an element

flux

transfer of element from one pool to another

carbon sink

reservoir that absorbs more carbon than it releases

carbon source

reservoir that releases more carbon than it absorbs

methanogenesis

certain waterlogged anaerobic conditions promote methane formation, involves 3 types of bacteria

the greenhouse effect

an increase in greenhouse gases in the atmosphere (methane, carbon dioxide, water, nitrous oxides, CFCs) traps short wave light energy from rebounding back into space as long wave radiation

ocean acidification

carbon dioxide enters the ocean and stops a reaction that allows shells to form

coral bleaching

ocean heats up, increasing algae photosynthesis reaction productivity, too much oxygen, algae is ejected off coral, coral loses its colourful algae and turns white, ruins symbiotic relationship.