Definitions Ecology defined by interactions and interconnections – with own species, other species, environment; organisms affect each other, environment; environmental factors affect organisms and activities. Ecology defined by interactions and interconnections – with own species, other species, environment; organisms affect each other, environment; environmental factors affect organisms and activities. Organisms and envt. factors: Organisms and envt. factors: Species - group of actively or potentially interbreeding individuals reproductively isolated from other such groups Population - all individuals of a species in a discrete area Community – a group of populations of species that occur together and interact Ecosystem – functional unit; community and surrounding physical and chemical environment. –Large, complex, component studies –Ocean ecosystems – different physico-cemical factors, different biotic effects, –Drives adaptation, changing composition

Energy - Trophic Structure Autotrophs standing crop/biomass standing crop/biomass productivity productivityHeterotrophsDecomposers Food chain Trophic levels Food web

Biogeochemical cycles

Carbon Cycle Source Source Sink Sink Self limiting feedback Self limiting feedback

Limiting factors Energy – how it enters, how it moves, where is it stored Energy – how it enters, how it moves, where is it stored Abiotic factors – tolerance range for physical, chemical Abiotic factors – tolerance range for physical, chemical Interactions with other organisms Interactions with other organisms

Niche - ecological role of a species in the community Fundamental niche – all the ecological conditions where an organism could exist, roles it could play Realized niche – actual conditions where organism does exist, roles it does play (real world distribution) Niche Breadth - range of conditions tolerated or resources used by an organism Specialist – narrow range of conditions tolerated, resources used Specialist – narrow range of conditions tolerated, resources used Generalist – broad range of conditions tolerated, resources used Generalist – broad range of conditions tolerated, resources used – place where an organism is found (more general) – place where an organism is found (more general) Environment

Niche Realized niche Fundamental niche Salinity Temperature

Interaction Reproductive potential >> natural population. Limits to explosive growth? Competition Competition Predation Predation Parasitism and disease Parasitism and disease

Competition – interaction among organisms for a necessary resource that exists in short supply - Interspecific - Intraspecific - Intraspecific Interference - one individual exerts negative effects/actively prevents another from getting resources Interference - one individual exerts negative effects/actively prevents another from getting resources Exploitation - one individual exploits a resource at a higher rate than another (less direct) Exploitation - one individual exploits a resource at a higher rate than another (less direct)

Competitive exclusion principle (Gause’s principle 1934) – no 2 species with the same requirements can exist in the same space at the same time

Niche overlap competition outcomes. Competitors coexistCompetitors coexist Stronger competitor displaces weakerStronger competitor displaces weaker

Conditions for Coexistence: – magnitude of competitive effect on both is low (food supply, abiotic conditions) – magnitude of competitive effect on both is low (food supply, abiotic conditions) – superior competitor is kept at low densities – superior competitor is kept at low densities Competitive relationships: hierarchical A > B > C networkA > B, B > C, but C > A

Community structure – make-up of species in a community Species richness – number of species Species evenness – distribution of individuals among the species “Diversity” combines richness and evenness Dominant species – species with greatest number of individuals or biomass Species NumberNumber NumberNumber

Population limiting factors – biological and physical Density-dependent Density-dependent Density-independent Density-independent Leibig’s Law of the Minimum – that life requirement or essential resource that is first reduced below the minimum (in shortest supply) will limit growth and survival Resource renewal – can be active or passive, rate affects population growth

Exponential growth – growth without limits

Logistic growth – density-dependent growth

Predation – Predators can prevent competitive exclusion, allow coexistence Predator avoidance strategies rapid reproduction rapid reproduction refuges refuges Optimal foraging theory – predators select prey to maximize rate of food intake

Predation : consumption of one organism by another Effect can vary Effect can vary –Large change in prey density = predatory control (Paine’s starfish) –Little/no change = little control effect (least tern) Keystone species Keystone species Trophic cascade Trophic cascade

Figure 5: CPUE per lunar month of Stolothrissa and Lates stappersii (mukeke)

Predation: a force to structure communities -- Pisaster, a starfish, keystone predator. in the absence of Pisaster, a few competitive dominants (barnacles and mussels) can usurp all the space in the intertidal. Pisaster predation can free up areas of rock that can then be used by other species such as anemones. 2) Sea otters reduce sea urchins and increase kelp -- The kelp "forests", in turn, provide habitat complexity, prey refuges and spawning sites (e.g., for herring) that seems to increase the diversity of species that can exist.

Population life history strategies A continuum; two types (MacArthur) define extremes. A continuum; two types (MacArthur) define extremes. Opportunistic or R-strategy – short life, rapid maturity, many reproductions/yr., high death rates, larvae usually present. Usually, small, sedentary and inefficiently use resources, poorer competitors. Highly variable numbers Opportunistic or R-strategy – short life, rapid maturity, many reproductions/yr., high death rates, larvae usually present. Usually, small, sedentary and inefficiently use resources, poorer competitors. Highly variable numbers Equilibrium or K-strategy – long life, long development time to maturity, proliferate slowly, ne or few reproductions/yr., low death rates. Usually larger than opportunists, mobile, efficiently use resources, better competitors. Fairly constant numbers. Equilibrium or K-strategy – long life, long development time to maturity, proliferate slowly, ne or few reproductions/yr., low death rates. Usually larger than opportunists, mobile, efficiently use resources, better competitors. Fairly constant numbers.

Opportunists favored where disturbance is frequent (waves, sedimentation, predators). Why? Opportunists favored where disturbance is frequent (waves, sedimentation, predators). Why? Why do bottom samples usually contain both types? Why do bottom samples usually contain both types? Why do proportions change over an area? Why do proportions change over an area? Why do the change with depth? Why do the change with depth?

Password is wfb279 For Thursday read For Thursday read Strathman “Why does a larva swim so long?” and Strathman “Why does a larva swim so long?” and Vance “Reproductive strategies in mrien benthic invertebrates” Vance “Reproductive strategies in mrien benthic invertebrates”