Transcript Communities, Ecosystems, and Biodiversity

Communities, Ecosystems,
and Biodiversity
Definitions of community
Organism interactions
Ecosystems
Different types of communities, ecosystems
Biodiversity
Community Definitions
All organisms in an area
Also includes: interactions, structure, organization
Can also include recurrence
The biological component of ecology (interactions
between an organism in an area plus the environment)
Superorganism (Clements, 1926) vs.
Individualistic responses (Gleason, 1929)
Organism Interactions
Competition
Food, space, nutrients, light
Niche concept and guilds
Dominance
Organisms partition resources so don’t compete
Dominant organisms
Organism Interactions
Predation
Hunting: chemosensory, visual
predator avoidance
Morphology, chemistry, behavior
Predators and trophic pyramids
Organism Interactions
Epibiosis
relationships: mutualists, parasites, commensal
Keystone species and “species of great effect”
Why study marine
communities?
Understand trophic web
Recognize keystone species, species of great effect
Conservation practices
Fisheries impacts, sustainable harvesting
Importance of previously unknown processes
Microbial loop, primary productivity and iron
Understand impact of pollutants
Example: Sea Grass Bed, TX
Annually dynamic, but over time, averages out to similarit
Dead versus live assemblage comparisons
In current near estuary, fully marine
Example: Sea Grass Bed, TX
Sea grass: baffles sediment:
environment mediator, species of great effect
Clams, gastropods, polychaete worms, arthropods, others
Larval settlement at different times of year per species
Clams in spring
Summer: many dead juvenile clam shells in sediment
Seagrass, algae: primary producers
Gastropods: grazers, predators
Clams: detritovores
Mussels and polychaetes: filter feed
Arthropod and fish: predators
Seagrass substrate for microbes, algae
Microbial loop recycles nutrients
ECOSYSTEM
Ecosystem = community + environment
Scaless
Environment = physical aspects
Topography, sediment type, currents, light
Often anthropogenic effects: pollutants, sediments
Dynamic: always changing on fine temporal scales
Over geologic time: slow and quick changes
Example: Hydrothermal Vents
Deep ocean, near “black smokers”
Very high T water, sulfur, other chemicals
No light, low O2
Tube worms, bivalves, shrimp, crabs, eels
Symbiotic relationship with sulfur-fixing bacteria
Similar to photosynthesis, but some predation
Nutrient input from smokers, detritus
Organisms tightly coupled with environment
Open or closed system? Patches far apart, smokers ltd time
Organisms have to get there somehow!
Biodiversity
Species richness: how many species
Can be studied on community/ecosystem scale or globally
Ocean extremely diverse
Reefs more diverse than rainforest!
Most of study of biodiversity through time marine
Diversity greatest on continental shelves, coasts
Light, nutrients --> primary productivity high
Diversity in deep ocean also high
Nutrients, O2
But…patchy
Extinctions
Local extirpations --> global extinctions
Small, background extinctions --> mass extinctions
Background extinctions:
local to regional; one or few species
Causes of background extinction:
Speciation, outcompete, invader, environment, disease
Mass Extinctions
Involve MANY species, global
5 major mass extinctions:
Largest: P/Tr, 250MYA – 80 to 95% marine life
Most well known: K/T, 65MYA – 40% marine life
Mass Extinctions
Causes of mass extinction:
Climate change
ocean circulation change
Volcanism
Extraterrestrial impact
Sea-level change
Human factors
A human-caused mass
extinction?
Trophic changes