Ecological niches - B4.2

ecological niche definition

• the role of a species in an ecosystem

• made up of many factors → unless all the dimensions of a niche are satisfied in an ecosystem a species will not be able to survive, grow or reproduce

biotic factors that influence growth, survival and reproduction → ecological niche

• e.g food supply → autotrophic or heterotrophic.

• To minimize competition species become specialists in sourcing food. → adaptations are required

• e.g utilization of other species to provide a wide range of services such as pollination of flowers

abiotic factors that influence growth, survival and reproduction → ecological niche

zones of tolerances for abiotic variables determines the habitat of a species → where it lives in an ecosystem

obligate aerobes

• need oxygen as they cannot ferment or respire anaerobically.

• They gather at the top of a tube with water where oxygen concentration is the highest

• e.g all plants + animals

obligate anaerobes

• poisoned by oxygen

• gather at the bottom of a tube with water where the oxygen concentration is the lowest

facultative anaerobes

• can metabolise energy aerobically or anaerobically

• gather mostly at the top of a tube with water as aerobic respiration generates more ATP than fermentation

Photosynthesis

energy from light is used for fixing carbon dioxide and making carbon compounds such as sugars and amino acids which create the basis of life.

3 groups of organisms that use photosynthesis

• plants

• eukaryotic algae

• cyanobacteria (bluegreen bacteria)

heterotrophic nutrition

• gain a source of organic molecules by consuming another source of organic molecules

• all animals are heterotrophic

Holozoic nutrition

• food is ingested, digested internally, absorbed and assimilated

• sub group of heterotrophic nutrition

Autotrophic nutrition

gains nutrition by using a source of energy to convert inorganic molecules (carbon dioxide, water) into organic molecules (glucose)

Mixotrophs definition

organisms that can obtain energy and carbon through both autotrophic and heterotrophic nutrition. e.g Euglena

facultative mixotroph

can function as autotrophs, heterotrophs or both. Depending on environmental conditions

obligate mixotroph

require both autotrophic and heterotrophic nutrition in order to survive

mixotrophy advantages

• flexibility: Organisms can adapt to nutrient availability, surviving in both nutrient-rich and nutrient-poor environments.

• Energy Efficiency: Mixotrophs maximize energy intake by switching between modes as conditions change.

Saprotrophic nutrition

• a mode of heterotrophic nutrition where organisms gain nutrition by feeding on dead or decaying organic material by secreting digestive enzymes into the food source (extracellular digestion) and absorbing the products of digestion.

• fungi + bacteria that use saprotrophic nutrition can be referred to as decomposers

Archaea

• one of the 3 domains of life (Bacteria, Eukaryotes, Archaea)

• metabolically very diverse

• group of micro-organisms that are similar to, but evolutionarily distinct from bacteria

• use either light, oxidation of inorganic chemicals or oxidation of carbon compounds to provide energy for ATP production

Chemoheterotrophs

• obtain energy through oxidation of carbon compounds obtained from other organisms

• carbon compounds are obtained through other organisms (not photosynthesis)

Photoheterotrophs

• obtain energy through absorption of light using pigments (not chlorophyll)

• obtain carbon compounds from other organisms (not photosynthesis)

Chemoautotrophs

• obtain energy through oxidation of inorganic chemicals (chemical reactions)

• obtain carbon compounds through anabolic reactions from carbon dioxide

Paranthropus robustus - members of Hominidae family

• lived 1-2.6 million years ago

• Large molars

• Wide large lower jaw

• skull has sagittal crest along the midline → suggests strong chewing muscles

• broad herbivorous teeth

• → suggests that they ate plant foods and tough grasses and seeds

Homo floresiensis - members of Hominidae family

• lived 50,000-20000 years ago

• reduction in molar size + teeth (still bigger than homo sapiens)

• → suggests that they ate uncooked plant foods and meat

Homo sapiens → members of Hominidae family

• flat molars at back of mouth → crush food

• sharper canines + incisors

• → suggests that they eat both plants + meat

Sap-feeding herbivores

• Aphids

• piercing mouthparts → allow piercing of plant shoot + feeding on phloem sap

Chewing herbivores

• Beetles

• jaw-like mouth parts

• tough mandibles for biting off, chewing and ingesting leaves

Plant defenses against herbivory

• sharp spines + thorns (e.g Roses) that can injure herbivores

• secondary metabolites that act as repellents or toxins (Acacia trees)

• mutualistic relationships with ants to repel herbivores (Acacia trees)

herbivore counter adaptions

• some herbivores have evolved metabolic adaptations to counteract plant defenses.

• detoxification of enzymes → neutralise toxic compounds

• Specialised feeding habits → feed on specific plants

vampire bats physical, behavioural and chemical adaptations

• physical:

• razor sharp teeth

• expandable stomach → can quickly process food

• Behavioural:

• target sleeping animals + often return to the same individual

• Chemical:

• saliva contains anticoagulants which prevents preys blood from clotting

black mamba physical, behavioural and chemical adaptations

• Physical: fast (19 km/h) → can pursue prey

• Behavioural: bite + release prey to avoid injury from struggling animals

• Chemical: rapid acting neurotoxins causing rapid paralysis of prey.

Koala physical, behavioural and chemical adaptations

• Physical: sharp claws + teeth for protection against predators

• Behavioural: Arboreal life-style → avoid ground dwelling predators

• Chemical: eat toxic leaves that other animals are unable to digest → taste unpleasant to potential predators

adaptations of trees in canopy layer for harvesting light

• thin trunks + rapid vertical growth

• crowns spread widely to maximize surface area exposure to sunlight

adaptations of lianas for harvesting light

• use existing trees for support → use tendrils + hooks to reach the canopy without investing in structural growth.

• fast vertical growth → bypass competition on forest floor

adaptations of epiphytes growing on tree branches for harvesting light

• waxy + thick leaves → minimize water loss

• aerial roots → absorb moisture + nutrients from air

• long leaves → maximize light absorption

adaptations of strangler epiphytes for harvesting light

develop aggressive root systems that encircle and outgrow the host tree causing the tree to die leaving only the epiphyte.

adaptations of shade tolerant shrubs/herbs on forest floor for harvesting light

• large thin leaves → maximize surface area for light absorption

• high chlorophyll content → efficient photosynthesis

• slow metabolism → reduces energy demand

fundamental niche

• the potential of a species based on adaptations and tolerance limits

• species cannot survive beyond fundamental niche

realized niche

the actual extent of a species niche when in competition with other species

competitive exclusion principle

• In every ecosystem, species compete for limited resources such as food, water, space, and light.

• If two species depend on the same resource in the same way, one will eventually outcompete the other or will lead to the restriction of both species to a part of their fundamental niche.

niche partitioning

the process by which natural selection drives competing species into different patterns of resource use or different niches. (e.g using different areas of the same resource, temporal partitioning)