B4.2 Ecological Niches

Niche

Role of a species in an ecosystem

• Including where it lives

• What it eats

• What eats it

• Impact on environment

• What it does

• Encompasses everything the species interacts with - biotic and abiotic

Fundamental vs Realised niche

Fundamental niche: Potential niche species could occupy with no competition

Realised niche: Actual niche a species occupies in presence of its competitors

E.g. Chthamalus barnacles

• Fundamental: low tide + high tide

• Realised: Only high tide due to competition with Semibalanus barnacles.

Competitive exclusion

• When fundamental niches of 2 species overlap causes competition

• Which can lead to one species outcompeting the other, resulting in the exclusion of the less competitive species from that niche.

• Weaker species is eliminated

• E.g. 2 species of protozoans

  • Paramecium aurelia + Paramecium caudatum

  • aurelia survived and outcompeted caudatum

Niche partitioning

• The process by which competing species in fundamental niche coexist

• By utilising different resources or habitats to reduce competition

• Allowing them to occupy the same area without directly competing for the same resources

• Both become restricted to just part of fundamental niche

• E.g. Warbler birds inhabiting particular part of same tree

• E.g. Shore birds that share area on shore

Anaerobes + Aerobes

• Anaerobes survive in environments with no air/oxygen - eutrophication, polluted lake/soil

• Aerobes require oxygen to survive and thrive in oxygen-rich environments, such as the atmosphere.

• Organisms can be placed into 3 categories

  • Facultative anaerobes - optional and can survive in either environment

    • E.g. E. coli

  • Obligate aerobes - must have oxygen

    • E.g. humans, most animals

  • Obligate anaerobes - cannot survive in oxygen

    • E.g. Clostridium species

Autotrophic nutrition

• Produce own organic compounds from inorganic (self-feeding) - through photosynthesis or chemosynthesis.

  • Plants, algae, some bacteria

• Organisms such as plants and some bacteria that convert sunlight or chemical energy into food, forming the base of the food chain

  • Photosynthetic prokaryotes (Cyanobacteria) even tho there aren’t any organelles the whole thing is like a chloroplast

Adaptations of plants for harvesting light

• Lianas (type of plant): Climbs to the top by using other plants - top has more light

• Epiphytes: Germinate high up (not rooted in soil), grow on other plants, gaining access to sunlight without harming their host, get nutrients and water from air/moisture/host branch

  • not parasites but need a host plant

• Strangler epiphytes: Start same as epiphytes BUT grow long roots down, gradually enveloping it and competing for light, eventually shading out the host--killing it.

• Shade tolerant shrubs/herbs: These plants can thrive in low-light conditions, adapting their leaf structure and photosynthetic efficiency to maximize light capture in shaded environments.

Heterotrophic nutrition

• Obtain organic compounds from other compounds (feed on others)

  • All animals + All fungi

• Includes:

  • Holozoic (ingest food, digest, assimilate (incorporate into new material))

    • Amoeba, Humans

  • Saprotrophic (don’t ingest, release enzymes onto food to digest and absorb the digested food)

    • Fungi/Decomposers

Mixotrophic nutrition

• Organisms can obtain energy and nutrients through both autotrophic and heterotrophic means, such as some protists and plants.

• This allows them to adapt to varying environmental conditions.

• E.g. Euglena is a freshwater example

Archaea

• Archaea are very diverse with many methods of nutrition

• Main methods

  • Autotropic (not photosynthesis): absorption of light by pigments - not chlorophyll

  • Chemoautotrophic: oxidation of inorganic chemical substances to obtain energy (Fe2+—>Fe3+)

  • Heterotrophic:Obtain organic compounds from other compounds (feed on others)

Herbivores + their adaptations for eating

Organisms that primarily consume plants or plant-based materials for energy and nutrients, playing a key role in the food chain.

• Leaf eating insects - E.g. Aphid Insect

  • Chewing mouth part (mandibles)

  • Piercing mouth part (Stylets) used to suck up sap from phloem

• Mammals - E.g.

  • Specialised incisor for cutting

  • Flattened molars for chewing and grinding plant material, helping in the digestion of tough fibres.

Omnivores

Organisms that consume both plants and animals for energy and nutrients, contributing to various trophic levels in ecosystems.

Carnivores

Organisms that primarily consume other animals for energy and nutrients, often serving as predators in the food chain.

Predators

Organisms that hunt and kill other animals for food, playing a crucial role in controlling prey populations and maintaining ecosystem balance.

• Not all carnivores are predators - vultures do not kill

Adaptations of predators

• Physical: Stealth + speed, eagle spot prey from 3km away, Owl hears everything even tiny movements by mouth

• Chemical: Cone snail injects venom

• Behavioural: Dolphins hunt in packs

Prey

Organisms that are hunted and consumed by predators, playing a vital role in food webs and ecosystem dynamics.

• Adaptations

  • Physical: Rabbits have eyes on sides of head for 360 degree vision

  • Chemical: Skunk spray - pungent liquid from anal glands

  • Behavioural: population of mackerel form ball of fish to frighten predators

How can we tell what type of vore now extinct animals were

By examining their fossilized teeth and jaw structures, scientists can infer dietary habits and classify them as herbivores, carnivores, or omnivores.

• Carnivore: sharp teeth adapted for tearing flesh.

• Herbivore: flat teeth designed for grinding plants + mostly molars

• Omnivore: a combination of sharp and flat teeth for consuming both plants and animals.

Simpsons reciprocal index

A measure used in ecology to quantify biodiversity by taking into account the number of species and their relative abundance in a community.

• It helps assess the likelihood of randomly selecting two individuals of the same species.

Only works if:

• Population is closed (no deaths, immigrations, births,…)

• Sample is large enough

D = Reciprocal index

• Higher score = Higher biodiversity

N = total # of organisms

n = # of each species