B4.2 Ecological Niches

Ecological niche

Organism's home or habitat as well as its role in the ecosystem

- environment conditions organism, organism impacts environment

- adapted modes of respiration, nutrition, dentition, etc...

Resource partitioning

adaptations of organisms to fit into specific/unique niches and avoid competition

Zone of tolerance

range of abiotic and biotic conditions in which an organism can survive, determines niche

Specialist species

species adapted to narrow habitats, limited food resources, or other very specific environmental conditions

- narrow/specific niche

Generalist species

species adapted to and can survive in a variety of habitats, food resources and environmental conditions

- broad ecological niche

Obligate anaerobe

organism that can only survive in environments lacking oxygen

- use other compounds such as nitrates, sulfate, iron as electron acceptors in respiration

- oxygen is toxic to them (O2 is free radical, highly reactive), they lack certain enzymes to mitigate it

Ex. clostridium difficile, tetanus

Facultative anaerobe

organism that can survive in both environments lacking or rich in O2

- when oxygen is present they respire, when it is absent they ferment

- respiration is preferable due to higher ATP yield

Ex. E. coli, yeast

Obligate aerobe

organisms that can only survive in environments that contain oxygen

- require O2 as final electron acceptor to carry out respiration

Ex. humans, most animals, M. tuberculosis

Autotroph

organism that can produce its own food, produces its own compounds for respiration using light or chemicals

Photoautotroph

organism that produces organic compounds using light energy through photosynthesis

- light energy --> chemical energy

Ex. plants, algae, cyanobacteria

Chemoautotroph

organisms that derive energy from the oxidation of inorganic compounds via chemosynthesis

- use inorganic materials (H2SO4, Fe) to produce organic compounds for energy

- chemicals instead of sunlight

Mixotroph

organisms that use a mix of different sources of energy or carbon (photosynthesis and/or heterotrophy)

Obligate mixotroph

organism that must use both modes of nutrition

- may be due to it lacking a vitamin or nutrient that it must receive from an outside source

Facultative mixotroph

organism that can be either fully heterotrophic or fully autotrophic, or a mix of both (has the capacity to do both)

- mode of nutrition depends on environment

Ex. almost all marine plankton (take in both CO2 and food), Chlamydomonas (can photosynthesize but also ingest food

Heterotroph

organism that cannot produce its own food, consumer

- must ingest nutrients from other organic sources

Saprotroph

organism that obtains nutrients by secreting enzymes followed by absorbing and assimilating the nutrients

- external digestion of dead organic material

- important to break down dead matter, recycle C and N (nutrients) --> niche, speed up decomposition process in environment

Ex. certain fungi (mushrooms), yeast

Parasites

organisms that obtain food from other organisms (hosts) without killing them

Holozoic nutrition

organisms that consume food via the process of ingestions, digesting and assimilating the nutrients

- internal digestion, food must enter the body before being digested

3 types: Herbivore, omnivore, carnivore

Explain the 5 steps of holozoic nutrition (ingestion, digestion, absorption, assimilation, eliminitation)

Ingestion: taking food into gut (digestive tract)

Digestion: breaking down large food molecules into smaller molecules

Absorption: transport digested food across plasma membrane of cells, into body's blood and tissues

Assimilation: use digested food to synthesize proteins and other macromolecules, making them part of body's tissues

Elimination: removing undigested material from the end of the gut, egestion

Nutrition in archeae

- extremely diverse (phototrophic, chemotrophic, heterotrophic)

- adapted to survive in extreme environments (extreme salinity (halophiles), extreme pH, high sulfur)

Relationship between dentition and niche

- many organisms are holozoic and need teeth to properly consume meals (mechanical digestion)

- a lot can be known about an organism from its dentition

- relationship between dentition and diet

- adaptations in teeth that allow organisms to be successful in their niche

Specialized dentition in herbivores

- need to chew fibrous plants and herbs

- flat, large molars

- reduced canines

- thick enamel

- more-developed, large jaw --> wider face

Specialized dentition in carnivores

- need to cut meat

- small, sharp teeth (incisors and canines)

- smaller, less developed jaw

Adaptations of herbivores

insects

- some insects developed a strong pair of jaw-like mouthparts to cut, crush, and chew food

- some insects feed off internal plant fluids, use straw-like, tubular mouthpart (stylet)

mammals

- long, flat incisors to cut

- large, flat molars to grind food in sideways motion (like cows or goats)

Adaptations of predators to kill prey

Physical

- speed, agility, sharp claws and teeth to hunt and capture prey

- digestive systems capable of breaking down meat

- finely-tuned sensory systems to detect prey

- camouflage, go undetected by prey

Chemical

- toxins, chemicals that poison or paralyze prey

Behavioral

- making sounds of distress, mimicking to lure prey

- collaboration of individuals, group hunting

Adaptations of plants to harvest light

- competition for access to light, limited by forest canopy

ex. Lianas: climbing plants, don't stop until they reach top of canopy

ex. Epiphytes: grow entirely on branches of another plant, stranglers can kill their host

Leaf modifications

- increased surface area: large, broad, thin leaves

- increased absorption of sunlight

- carpet of plants called herb layer, can tolerate low light conditions

Adaptations of plants to resist herbivory

- production of toxic secondary metabolites (phytochemicals) to prevent consumption, ex. terpenes, phenols, polyketides, alkaloids

Animal-plant warfare: back and forth evolutionary attacks, adaptations

- some animals evolved to have special enzymes to metabolize phytochemicals

- plants then evolved chemicals that become toxic only after ingestion to circumvent this

Physical adaptations to be unpalatable:

- thick, rigid leaves that are difficult to chew

- spiny thorns

- microscopic thorns (trichomes)

- hiding from predators, avoiding detection or being seen

Adaptation of prey to avoid or resist predation

Physical

- camouflage (avoid being seen by predators)

- speed and agility (to escape)

- physical defensie mechanisms (ex. hedgehog spines, bright colors and patterns to indicate toxic substances and deter predators)

- eyes that are set far apart to increase visual field to be aware of predators

Chemical

- noxious chemicals, toxic and injure/harm predators

- can be released into the air or water

Behavioural

- collaboration, groupwork (ex. ball of fish work together to look larger and scare predator or to protect individual members)

Fundamental niche

the range of environmental conditions in which a particular species can live

Realized niche

the environmental conditions in which species actually live

- smaller than fundamental niche

- takes into account other constraints (factors) that make the actual niche much smaller

- conditions where the organism is best adapted and is able to live and reproduce

Competitive exclusion principle

- when there is more than one species in need of the same resource --> competition

- principle states that: if two species with identical niches compete, then one will inevitably drive the other to extinction

- two species cannot occupy the same niche for a long period of time, one will be outcompeted

Niche partitioning

process by which competing species use the environment differently in a way that helps them to coexist

- competition causes adaptations for both species

- permits competing species to occupy similar niches

- 2 types: spatial and temporal partitioning

Spatial niche partitioning

organisms occupy different spaces in the same habitat

Temporal habitat partitioning

organisms rely on the same resources, but niches are separated by the time at which they are active