lecture 3 - ecology Flashcards
define ecology
The relationships between organisms and their physical surroundings
biosphere
all living things on earth
biome
larger ecosystem (ocean)
ecosystem
- “A dynamic complex of plant, animal and microorganism communities and the abiotic (non-living portion) environment, interacting as a functional unit”
- Influenced by abiotic factors like temperature, nutrient availability, humidity, pressure, pH, O2 concentrations, etc.
community
Interacting populations of different species
occur in same geographic location at same time
Communities form part of the larger ecosystem
ex) the microbial community on your left elbow
population
a group of individuals of the same species occupying a region.
Frequently defined by geography
-Prairies vs. forests (Bison bison)
-Lung vs. gut (P. aeruginosa)
Niche
- An organism’s habitat and food requirements
- E. coli thrives in the mammalian intestine, can eat glucose and lactose - An organisms’ functional role within the ecosystem
E. coli uses O2, thus contributes to keeping the intestine anaerobic
**influenced by abiotic and biotic factors
mutualism
Organisms living in a mutually beneficial relationship
ex) Human host and bacteroides in intestine
commensalism
relationship benefits one organism and the other is unaffected (is any interaction ever neutral?)
ex) Human and Haemophilus influenzae in ear - usually benign –> can protect against staphococcus (mutualism) or can be parasitism too
parasitism
host is harmed in some way while the parasite benefits
what is nutrient acquisition? what type of relationship is this?
cows eat grass, bacteria in their stomach break down grass (cellulose) into fatty acids and protein, cow digests these NOT grass
**mutualism
when do competitive interactions occur
- overlaping niches cause competition for resources (food, space, minerals)
- ability to compete influences number of organisms
- can cause exclusion of a species from an environment which can be problematic
ex) c.diff is minor member of gut community - over use of antibiotics removes competitors and it had ability to overgrow creating GI issues
what is meant by: species within an ecosystem are interconnected and interdependent
Changes that influence one species can, through relationships with other species, result in changes throughout the entire community and ecosystem
what is succession? and how does it occur
changes in community structure.
-caused by changes in environmental conditions (internal - seasonal,nutrients, host age, external - antibiotics)
what are the consequences of succession?
- changes are unanticipated and occur at various scales
- c.diff overgrowth d/y antibiotics killing normal gut flora
what influences chance of encountering microbes?
microbe distribution (where in environment)
what influences likelihood of infection?
micrbe abundance (how many it takes to cause infection) -infectious dose
autotroph
Uses inorganic CO2 as its carbon source (not nutritionally dependent on other living things)
-Photosynthetic organisms like plants
heterotroph
Must obtain carbon in organic form (nutritionally dependent on other living things)
Humans, E. coli
chemotroph
organic molecules as energy
phototroph
uses light as energy
lithotrophs
uses inorganic molecules (H2S) as energy
aerobes
use oxygen for metabolism, and have antioxidants
obligate aerobes
require O2 (humans)
-grow at air-liquid interface
Facultative anaerobe
optimal growth in O2, but can grow without O2
-E. coli, Salmonella
-grow throughout tube
Micro-aerophile
grows at lower O2 concentrations
ex)Campylobacter jejuni
anaerobes
don’t have metabolic enzymes for using O2
Obligate anaerobes
are killed by O2
ex) Bacteroides (dominant bacteria in healthy human gut)
- grow below surface, away from O2
Aerotolerant:
don’t require O2 but can survive in environments with oxygen.
-some members of Clostridium
what factors do microbes require for growth?
temperature, pH, salinity
- affects where microbes can grow, can only grow optimally in a small range of conditions
- can survive small fluctuations in conditions
