b4.2 - ecological niches

ecological niche

each species in an ecosystem fulfils a unique role and has both biotic and abiotic elements

- multidimensional

zones of tolerance for abiotic variables

determine the habitat of a species - where it lives in the ecosystem

in order to minimise competition, species must

specialise by developing adaptations for the mode of nutrition

unless all the dimensions of a niche are satisfied..

a species will not be able to survive, grow or reproduce

obligate aerobes

require a continuous oxygen supply so they only live in oxic environments

- all animals and plants

obligate anaerobes

inhibited or killed by oxygen

- methanogenic archaea

examples of anoxic environment

swamps, water-logged soils or muds

facultative anaerobes

use oxygen if available so they live in oxic or anoxic environments

- E coli, yeast

what is photosynthesis

energy from sunlight is used for fixing carbon dioxide and using carbon from it to produce sugars amino acids and other carbon compounds

three groups of photosynthesizers

- plants including mosses, ferns and flowering plants

- eukaryotic algae - seaweed + chlorella

- groups of bacteria - cyanobacteria

what domain of life does photosynthesis not occur in

archaea

- can occur in eukaryotes and bacteria

heterotrophic

Organisms that obtain their nutrients or food from consuming other organisms.

Holozoic nutrition

whole pieces of food are swallowed before being fully digested

ingestion

taking the food into the gut

digestion

breaking large food molecules into smaller molecules

absorption

transport of digested foods across the plasma membrane of epidermis cells and thus into the blood and tissues of the body

assimilation

using digested foods to synthesize proteins and other macromolecules and thus making them part of the body's tissues

egestion

voiding undigested material from the end of the gut

autotrophs

make their own carbon compounds from simple substances including carbon dioxide

facultative mixotrophs

can be entirely autotrophic, entirely heterotrophic, or use both modes

- Euglena gracilis

how is euglena gracilis a facultative mixotroph?

- has chloroplasts and carries out photosynthesis when there is sufficient sunlight

- can also feed on detritus or smaller organisms by endocytosis

obligate mixotrophs

cannot grow unless they use both autotrophic and heterotrophic modes of nutrition

saprotrophs

secrete digestive enzymes into the dead organic matter and digest it externally, then they absorb the products of digestion

decomposers

fungi and bacteria

- they break down carbon compounds in dead organic matter and release elements such as nitrogen into the ecosystem, allowing them to be used again

three domains of life

bacteria, eukaryotes, archaea

archaea - ATP production

very diverse energy sources

- phototrophic: absorption of light energy by pigments, other than chlorophyll

- chemotrophic: oxidation of inorganic chemicals

- heterotrophic: oxidation of carbon compounds obtained from other organisms

herbivore teeth

large and flat to grind down fibrous plant tissues

omnivore

tend to have a mix of different types of teeth to break down both meat and plants

- flat molars in the back of their mouth to crush and grind

- sharper canines and incisors than herbivores to tear tougher food

two groups of herbivore insects

- beetles and other insects with jaw-like mouthparts for biting off, chewing and ingesting pieces of leaf

- aphids and other insects with tubular mouthparts for piercing leaves or stems to reach phloem sieve tubes and feed on sap

ways plants deter herbivores

- tough sharp-pointed spines, so herbivores risk injury when eating

- stings to cause pain

- plants can synthesise toxic substances called secondary metabolites which are stored in seeds

- some animals develop metabolic adaptations to detoxify them

why are seeds attractive to herbivores

they have a high concentration of protein and starch or oil

behavioural adaptations

change relatively quickly

physical adaptations

take longer to develop because there must be genetic change

chemical adaptations

slowest to change, because new enzymes may be needed or new ways of regulating enzymes

forest canopy

trees have a dominant leading shoot that grows rapidly to great height to reach the forest canopy where they are unshaded by other trees

lianas

vine which uses other trees from support

- therefore they do not produce as much xylem tissue (wood) as free standing trees

epiphytes

grow on the trunks and branches of trees, so they receive higher light intensity than if they grew on the forest floor

- however, they have minimal soil for their roots

strangler epiphytes

climb up the trunks of trees, encircling & outgrowing them to shade out the leaves of the tree; eventually the tree dies, leaving only the epiphyte

shade tolerant shrubs and herbs

absorb light reaching the forest floor

fundamental niche

the potential of a species based on adaptations and tolerance limits

realized niche

the actual extent of the fundamental niche that a species occupies

- subset

if two species in an ecosystem have overlapping fundamental niches and one species outcomes the other in all parts of the fundamental niche...

the outcompeted species does not have a realised niche and will be competitively excluded from the whole ecosystem