B4.2 Ecological Niche

Factors affecting the niche of species

BIOTIC factors

• include living things

• food availability, predators

ABIOTIC factors

• temperature, soil nutrients, light, and other non-living factors

Niche Construction

the process by which an organism alters its own or other species local environment

• ex: earth worms chemically + physically modify the soil, thus other aquatic animals can live on the land

Types of Ecological Niches

Fundamental niche

• niche of an org. when there are no limiting factors on the environment + resources the organism can use

• theoretical, pre-competitive

• potential of a spp based on adaptations + tolerance limits

Realized niche

• niche that’s occupied by a viable population of a species in the presence of competitor spp

• post-competitive, actual

• actual extent of a spp when in competition with other spp

Competitive exclusion

two diff spp cannot occupy the same niche → if 2 spp share a niche, this leads to INTERSPECIFIC COMPETITION for resources

• inevitably, 1 spp will hv an advantage over the other

• the less well-adapted spp will struggle to survive and reproduce

Resource Partitioning

2 spp can avoid competing for the same resource by choosing different time for feeding or different foraging behavior

Types of Resource Partitioning

• temporal

  • same resources but diff time

• spatial

  • use of diff habitat of resources

• morphological

  • use of body shape + size

Importance of ecological niches

• niches reduce competition for resources

• interspp competition → evolutionary change

• niche includes spot in food chain (if missing → may cause whole chain to die)

• segregation of organisms into niches avoids confusion of activities in the community + more order

• allows for full exploitation of all available resources

Differences b/t obligate anaerobes, facultative anaerobes, obligate aerobes

Obligate Aerobes: require O2

Obligate Anaerobes: killed by O2

Facultative Anaerobes: grow better with O2 but can live without it

Mode of Nutrition in different organisms

an organism’s mode of nutrition depends a lot on its ecological niche + the adaptations to the biotic and abiotic factors

Autotroph

• synthesize organic compounds (sugar, aa, fats) by using other sources of energy

  • photoautotroph

    • produce organic compounds from CO2, water, and light energy thru PS

  • chemoautotroph

    • producce org. compounds from other elements (iron, NH3) thru chemosynthesis

Heterotroph

• obtain org. compounds by consuming other organisms internally or externally

  • saprotrophs

    • secrete enzymes onto dead + decaying matter and digesting externally (decomposer)

  • parasites

    • obtains food from other organism without killing it

  • holozoic

    • complex food particles are taken in and broken down

    • herbivore

    • carnivore

    • omnivore

    • detritivore (an animal that feeds on dead organic material, especially plant detritus)

Mixotroph

• organism that uses a mix of different sources of energy and carbon, instead of having a single trophic mode, on the continuum from complete autotrophy to complete heterotrophy

Photosynthesis as the mode of nutrition in plants, algae, and several groups of photosynthetic prokaryotes

algae, seaweed, kelp, many types of bacteria, plants

Holozoic (obtaining nourishment as animals do by ingesting complex organic matter) nutrition in animals

animals obtain their nutrients by consuming food

the large food molecules must be broken down into smaller ones before they can be absorbed into the bloodstream + transported to cells in the body where needed

• ingestion: eat

• digestion: breaking down food

• absorption: moving food into cells

• assimilation: making food part of cells

• elimination/egestion: remove unused food

single celled organisms like amoeba can do holozoic nutrition even w/o multi-organ controlled digestive system by endocytosis/engulfment

Autotroph

synthesize organic compounds (sugar, aa, fats) by using other sources of energy

• photoautotroph

  • produce organic compounds from CO2, water, and light energy thru PS

• chemoautotroph

  • producce org. compounds from other elements (iron, NH3) thru chemosynthesis

Heterotroph

obtain org. compounds by consuming other organisms internally or externally

• saprotrophs

  • secrete enzymes onto dead + decaying matter and digesting externally (decomposer)

• parasites

  • obtains food from other organism without killing it

• holozoic

  • complex food particles are taken in and broken down

  • herbivore

  • carnivore

  • omnivore

  • detritivore (an animal that feeds on dead organic material, especially plant detritus)

Mixotroph

organism that uses a mix of different sources of energy and carbon, instead of having a single trophic mode, on the continuum from complete autotrophy to complete heterotrophy

• can do PS

• can consume other organisms

FACULTATIVE MIXOTROPH

• CAN BE entirely autotrophic, entirely heterotrophic, or use both modes

OBLIGATE MIXOTROPHS

• MUST USE both modes of nutrition. often the case if a type of nutrient cannot be synthesized by themselves

Different Stages of Holozoic Nutrition

Ingestion

• take food into body

Digestion

• breaking down food

Absorption

• moving food into cells

Assimilation

• making food part of cell

Elimination

• removing unused food

many single celled organism such as amoeba are also capable of holozoic nutrition (even without a multi-organ controlled digestive system)

Saprotrophic nutrition in some fungi + bacteria (part of heterotrophs)

fungi are also called decomposers, bc they break down DOM and release important elements back into the ecosystem. extracellular enzymes are released into the substrate + break down polymers

bacteria are also saprotrophs by digesting food thru secretion of enzymes to break down OM externally. the products are then absorbed

Diversity of nutrition in archaea

phototrophic, chemotrophic, heterotrophic

Relationship between dentition and the diet of omnivorous and herbivorous representative members members of the family Hominidae

teeth give a lot of info about the feeding style of an individual

• herbivores: large + flat to grind fibrous plant material

• omnivores: hv mix of diff types of teeth to break down both meat + plants in their diet

  • molars: flat to crush seeds

  • incisors: for slicing (in the front)

  • canines: used for tearing

Adaptations of herbivores for feeding on plants

most insects are herbivores

• those with jaw-like mouthparts for biting off, chewing, and ingesting pieces of leaf

• those with tubular mouthparts for piercing leaves or stems to feed on the phloem sap

aphids hv modified piercing mouth parts called stylets.

• these secrete enzyme pectinase to break down polysaccharide pectin which holds tgt the cell wall of plants. that way the style can easily pass thru to sap

herbivorous animals (cows + sheep)

• have specialized back teeth

• their digestive systems are adapted to digesting plant matter

  • bacteria + archaea living in the rumen help to break down cellulose

Adaptations of plants for resisting herbivory

• castor beans produce seeds that contain ricin, which is highly toxic

• toxins that cause nausea, cardiac problems, or hallucinators when ingested

• plants have spikes/thorns

• plants detract/move, scaring animals away

Adaptations of predators for finding, catching, and killing prey

Finding Prey

• Enhanced senses: Acute vision (eagles), hearing (owls), smell (sharks), or electroreception (platypus)

• Specialized detection: Infrared heat sensing (pit vipers), echolocation (bats)

• Camouflage: Disruptive coloration allows predators to remain hidden while stalking prey

Catching Prey

• Speed and agility: Cheetahs (70 mph sprints), peregrine falcons (240 mph dives)

• Ambush tactics: Trapdoor spiders, anglerfish with luminescent lures

• Specialized appendages: Sticky tongues (chameleons), modified limbs (praying mantis)

• Pack hunting strategies: Wolves, lions, orcas use coordinated attacks

Killing Prey

• Mechanical adaptations: Sharp teeth/claws (big cats), powerful jaws (crocodiles)

• Venom delivery systems: Fangs (snakes), stingers (scorpions), spines (lionfish)

• Digestive enzymes: Spider venom liquefies prey internally

• Constriction: Pythons and anacondas restrict blood flow to prey's vital organs

Adaptations of prey for resisting predation

Defensive Structures

• Shells (turtles), spines (porcupines), exoskeletons (beetles)

Avoiding Detection

• Camouflage (stick insects), mimicry (viceroy butterfly)

Escape Mechanisms

• Speed (gazelles), flight, autotomy (lizard tail shedding)

Chemical Defenses

• Toxins (poison frogs), noxious secretions (skunks)

Behavioral Adaptations

• Alarm signals, group living (herds), mobbing behavior

Reproductive Strategies

• High reproductive rates, synchronized breeding events

Adaptations of plant form for harvesting light

Plants in very dense forests (like rainforests) hv to develop adaptations to harvest light for photosynthesis

• epiphytes get up into the understory/canopy to access sunlight. their roots attach to the tree trunks and collect water trickling along the branch

• vines can climb up the trunk of the tree

• large surface area of leaves help plants in the shrub layer of the forest to catch light

• lianas are vines that take root on the forest floor + use trees as a scaffold to grow up high into the canopy