B4.2 Ecological niches (CTs) Flashcards
(24 cards)
Define a niche
The unique role that a species plays in a community and where the organism lives (habitat)
Biotic and abiotic interactions
Ecological niches have biotic and abiotic elements
1. zones of tolerance for abiotic (non-living) variables determine the habitat of a species
- food is obtained either by synthesis using light, water & co2 OR by taking it in from other organisms
- to minimise competition, species must specialise & develop adaptations for their mode of nutrition
- other species are utilised to provide a diverse range of services
Unless all dimensions of niche are satisfied in an ecosystem, a species will not be able to survive, grow or reproduce
Difference in oxygen requirements between obligate anaerobes, facultative anaerobes, obligate aerobes
Obligate aerobes: require a constant oxygen supply so they only live in oxic environments (eg all animals & plants) –> most eukaryotes
Obligate anaerobes: inhibited/ killed by oxygen so only live in anoxic environments (lives in deep ocean, still water, intestinal tracts)
Facultative anaerobes: use oxygen if available so live in oxic/ anoxic environments (eg ecoli, yeast)
State the energy and carbon sources utilised in photosynthesis by prokaryotes
Energy from sunlight is used for fixing carbon dioxide & using the carbon from it to produce sugars, amino acids, and many other carbon compounds
List three groups of photosynthetic autotrophs
- plants (mosses, ferns, conifers, flowering plants)
- eukaryotic algae (seaweeds, unicellular algae lie chlorella)
- several groups of bacteria (cyanobacteria & purple bacteria)
Hence, photosynthesis occurs in two of the three domains of life: eukaryotes and bacteria but not in archaea
Outline the acquisition of energy and matter by holozoic animals
All animals are holozoic = heterotrophic
*holozoic is a type of heterotrophic
- animals obtain supplies of carbohydrates, amino acids and other carbon compounds by the consumption of food from other organisms
Molecules like polysaccharides & proteins must be digested before being absorbed
- digestion in most animals happen internally after food is ingested –> holozoic nutrition, where whole pieces of food are swallowed before being fully digested
*animals who digest food externally are not holozoic
Distinguish between ingestion, digestion, absorption, assimilation
Ingestion - taking the food into the gut
Digestion - breaking large food molecules into smaller molecules
Absorption - transport of digested food across plasma membrane of cells and thus into the blood and tissues of the body
Assimilation - using digested foods to synthesis proteins and other macromolecules and thus making them part of the body’s tissues
Egestion - removing undigested material from the end of the gut (NOT excretion)
Outline the acquisition of energy and matter by mixotrophic protists
Protists are unicellular eukaryotes
Mixotrophic protists use both methods (autotrophic and heterotrophic) of nutrition
State an example of a mixotrophic protist
Euglena gracilis is a well-known freshwater example of a protist that is both autotrophic & heterotrophic
- it has chloroplasts and carries out photosynthesis when there is sufficient light, but can also feed on detritus/ smaller organisms by endocytosis –> facultative mixotroph
Distinguish between obligate and facultative mixotrophs
Facultative mixotrophs can be entirely autotrophic, entirely heterotrophic or use both modes
Obligate mixotrophs cannot grow unless they utilise both autotrophic & heterotrophic modes of nutrition
- bc food they consume supplies them with a carbon compound they cannot themselves synthesise
Outline the acquisition of energy and matter by saprotrophic organisms
they secrete digestive enzymes into the dead organic matter and digest it externally, then they absorb the products of digestion
2 examples of saprotrophic organisms
- fungi
- bacteria
- fungi and bacteria with this mode of heterotrophic nutrition are referred to as decomposers bc they break down carbon compounds in dead organic matter & release elements like nitrogen into ecosystem to be reused by other organisms
3 domains of life
Archaea, Bacteria, Eukaryotes
Characteristics of archaea
- unicellular
- no nuclues (similar to bacteria) but in other aspects archaea are closer to eukaryotes
How archaea are very varied in how they obtain energy for ATP production
- phototrophic - absorption of light energy by pigments but pigments other than chlorophyll are used
- chemotropic - oxidation of inorganic chemicals
- heterotrophic - oxidation of carbon compounds obtained from other organisms
Hominidae family (omnivorous and herbivorous)
genera of extant: humans (Homo), orang-utans (Pongo), gorillas (Gorilla), chimpanzees (Pan)
extinct: Homo floresiensis, Paranthropus robustus
Teeth for different diet types
Herbivores - teeth tend to be large & flat for grinding down fibrous plant tissues
Omnivores - mix of diff types of teeth to break down meat & plants in diet
Humans - flat molars in back of mouth to crush & grind food, sharper canines and incisors than herbivores to tear tougher food
Hence, diet of extinct species in Homnidae can be inferred from their dentition
Outline the physiological, morphological, behavioural adaptations of leaf-eating insects for feeding on plants
*insect mouthparts show great diversity but are all homologous –> derived by evolution from same ancestral mouthparts
2 broad groups of leaf-eating insects:
1. beetles & other insects with jaw-like mouthparts for biting off, chewing and ingesting pieces of leaf
2. aphids and other insects with tubular mouthparts for piercing leaves/ stems to reach phloem sieve tubes and feed on sap
Outline the physiological, morphological and/ or behavioural adaptations of plants for resisting herbivory
- tough sharp-pointed spines / thorns
- stings which cause pain
- synthesise toxic secondary compounds in seeds and leaves (aka secondary metabolites)
- seeds are highly attractive to herbivores bc of their high concentrations of protein & starch/ oil
In some cases, herbivores have responded to toxic compounds in plants by developing metabolic adaptations for detoxifying them –> plant-herbivore specificity
Chemical, physical and behavioural adaptations of predators for finding, catching and killing prey
Physical: Vampire bats have unique dentition, with small premolars and no molars, but relatively large incisors and canines on upper jaw which are pointed & razor-sharp –> pierce prey so vampire can feed on blood
Chemical: Black mambas produce venom containing mixture of neurotoxins, incl inhibitor of acetylcholinesterase –> paralyses prey when injected via poison fangs then they swallow prey without resistance
Behavioural: Grizzly bears learn ambush strategies for catching migrating salmon either by trial and error/ copying others –> some wait at top of waterfalls for fish to jump out of water, others put head underneath water to watch for a fish swimming past
Chemical, physical and behavioural adaptations of prey for resisting predation
Physical: buff-tip moths resemble broken birch twigs –> camouflage when roosting during daylight hours on twigs/ on the ground –> this is when night-flying moths are most vulnerable to predation
Chemical: caterpillars of cinnabar moth feed on ragwort & accumulate toxic alkaloids from it; their black & yellow stripes are warning coloration which deter predators; adults are day-flying, with red & black warning coloration –> indicate they retain toxins obtained when larvae fed on ragwort
Behavioural: blue-striped snappers swim in a tight group, often with sudden changes of direction –> schooling behaviour reduces chance of predation, bc threats more likely to be detected and it is diff for predator to catch any one individual
Describe examples of adaptations for harvesting light, including height, lianas, epiphyte, shade-tolerance and leaf surface area
In environments where there is enough water for abundant plant growth and temperatures are suitable for photosynthesis, plants compete for light
1. trees have a dominant leading shoot –> grows rapidly to great height to reach forest canopy where they are unshaded by other trees
2. lianas climb through other trees, using them for support –> lianas do not need to produce as much xylem tissue (wood) as free-standing trees
3. epiphytes grow on the trunks and branches of trees –> receive higher light intensity than if they grew on the forest floor but there is minimal soil for their roots
4. strangler epiphytes climb up the trunks of trees encircling them and outgrowing their branches to shade out the leaves of the tree –> tree dies, leaving only the epiphyte
5. shade-tolerant shrubs and herbs absorb light reaching forest floor
Distinguish between fundamental and realised niche
Fundamental niche is the potential of a species based on adaptations and tolerance limits
- living organisms tolerate a range of biotic and abiotic conditions but their adaptations do not allow them to survive outside this range –> tolerance range is the fundamental niche
*if species living without any competitors, it wld occupy entire fundamental niche
Realised niche is the actual extent of a species niche when in competition with other species
- in natural ecosystem, there is competition and typically a species is excluded from parts of its fundamental niche by competitors
- actual extent of potential range that a species occupies is its realised niche
Competitive exclusion and the uniqueness of ecological niches
When fundamental niches of two species overlap, one species is expected to exclude the other from that part of its range by competition
- demonstrated experimentally with the flour beetles (Tribolium castaneum and Tribolium confusum)
- when reared tgt at diff combi of temp & humidity, T.castaneum usually excluded T.confusum in some combinations but T.confusum was more successful in other combinations
If two species in an ecosystem have overlapping fundamental niches, one species outcompetes the other in all parts of the fundamental niche, the outcompeted species does not have a realised niche and will be competitively excluded from whole ecosystem
- according to ecological theory, every species must have a realised niche that differs from the realised niche of all other species if it is to survive in an ecosystem
