448 midterm

critical period in early life history of fishes

time period when there is either match between larvae that need to find food and food or there is a temporal mismatch, determines the success of an entire cohort (either larvae lines up with phytoplankton bloom or does not - explains why there is only replenishment of fish populations every few years because of this match cycle)

Meiofauna examples

small annelids, larger protozoa (ciliates), some copepods

interference competition

physical attacks (like how Balanus overgrows Chthamalus)

exploitative competition

competing for the same resource (food, light, etc.) 

apparent competition

not a real form of competition, one prey species in proximity to another prey species attracts predators, bad for the species that wouldn’t attract predators naturally but ends up being preyed on because someone else attracted a predator 

green world hypothesis

“herbivores are seldom food limited and appear most often to be predator limited”Herbivores are not eating all the plants (hence why the Earth looks green), because they are preyed upon and their population is regulated

exploitation ecosystems hypothesis

 Productivity determines length of food chain across trophic levels - higher productivity can support more levels of predation

Conditions that promote trophic cascades

Simple food chains (no omnivory, cannibalism, or functional redundancy), low population connectivity, life history of prey-prey scale closely, homogenous habitat, common prey

Predation/disturbance intermediate disturbance hypothesis

Diversity is maxed at medium levels of disturbance/predation intensity - gradient between stress of competition vs environmental factors

Menge Sutherland model

• Regulatory mechanisms change among trophic levels

• Physical factors, competition, predation

• In a place with high environmental stress, physical factors matter most as regulatory mechanisms. In a medium stress zone, competition matters most. In a high stress zone predation matters most

Over-yielding

polyculture is more productive than the sum of the respective monocultures

Complementary hypothesis

Mechanism to achieve over yielding, different species access different resources in a complementary way

Non-transgressive over-yielding

Better than the average monoculture, but between that and the best monoculture

Transgressive over-yielding

beyond best performing monoculture

Idiosyncratic hypothesis

Explains 90% of Overyielding. Diversity produces higher function because the more species you acquire the more likely you are to get one high performing species that allows a gain of functionality

Functional diversity 

variety of biological roles or characteristics, reflects the
biological complexity of an ecosystem

Examples of functional classifications

habitat, trophic position, feeding mechanism

Saturdation/Redundancy hypothesis

Increasing species richness leads to diminishing returns in ecosystem functioning

Larval lottery hypothesis

adult species composition and communities are based on whatever larvae happened to arrive first when resources were available and became the best competitors for space (random - depends on who gets there early!)

Density dependent factors of population regulation

Limiting resources (food, space), predation, disease/parasitism

Density independent factors of population regulation

temperature, salinity, habitat destruction, etc. 

Demographically open paradigm of marine population connectivity

Outdated belief that all larvae of a species are in a connected pool and get mixed all together by ocean currents and then randomly land wherever

Demographically closed paradigm of marine population connectivity

More current belief that local larval retention limits population mixing (larvae likely become adults where they come from originally)

Main thing bottom up controls regulate

Productivity rates

Main thing top down processes regulate

standing stock biomass of lower trophic levels

wasp-waist ecosystem structure

Biomass structure forms a narrow ‘waist’ through which energy flow from low-high trophic levels is controlled - a short-lived intermediate species exerts top down and bottom up control, only seen in marine ecosystems
from low-to-high trophic levels is controlled due to one

F-ratio

the fraction of total primary production fuelled by nitrate or N-fixation
(“new” production) as opposed to ammonium, urea, AA, etc. (“recycled” production)

Habitat fragmentation

process by which a homogenous habitat is split into isolated smaller patches with a lesser total area 

habitat edge effects

changes in community structure or dynamics that occur at the boundary of two or
more habitats

fundamental niche

where an animal can reside based on just abiotic factors

realized niche

how an organisms niche shrinks based on biotic factors such as predation 

porifera

sponge phylum

• 5-10k species

• mostly filter feeders

• shallow water

cnidaria phylum

• jellies, corals, anemones

• complex life cycles (polyp, medusa stages)

annelid phylum

• segmented worms! mostly marine

• mostly benthic 

• 15k-20k species 

mollusks

• 100k species

• ubiquitous at all depths and latitudes

7 classes of mollusks

Cephalopods, gastropods, bivalves, Scaphopoda (tooth shells), aplacophora, monoplacophora (ancient limpets), polyplacophora (chitins)

arthropods

• 100k species 

• 10 classes 

echinoderms

• bilateral symmetry 

• 7500 current species, 15k in fossil records

chordata

• mostly epibenthic

• often filter feeders

Bergmann’s rule

Broadly it asserts that within a species the body mass increases with latitude and colder climate, or that within closely related species that differ only in relation to size that one would expect the larger species to be found at the higher latitude

Rapoport’s rule

Latitudinal ranges of plants and animals are generally smaller at low than at high latitudes

Thorsons rule

benthic marine inverts at lower latitudes produce more eggs and tend to have pelagic larvae, while those at higher latitudes produce fewer and larger yolk-feeding eggs and offspring

latitudinal emergence

deep-sea species at low latitudes are also found at shallower depths near the poles (i.e., the species follow an isotherm)

biodiversity portfolio effects

stability in aggregate community properties such as biomass or productivity generally
rises with species diversity, simply because of the statistical averaging of the fluctuations across species