B4.2: Ecological Niches

Ecological Niche

A species' unique role in an ecosystem, both biotic and abiotic

Species will survive, grow, and reproduce ONLY when all dimensions of the niche are satisfied in an ecosystem

Habit Determination

Determined by zones of tolerance for abiotic factors

Food is Obtained by...

Synthesis through using light, water, CO2

or

Consumption of other organisms

To compete effectively, organisms must specialize or develop adaptations

Three Domains

Archaea, Bacteria, Eukarya

Archaea

Unicellular and have no nucleus, can survive in extreme environment (high temp, low pH, high [salt])

Metabolically diverse regarding energy used for ATP production

-phototrophic, chemotrophic, or heterotrophic

*hard to culture in lab and less well researched*

Phototrophic

Absorption of light via pigments (not chlorophyll)

Chemotrophic

Oxidation of inorganic chemicals (Fe2+, Fe3+)

Heterotrophic

Oxidation of carbon compounds

Anoxic Environment

environment that lacks oxygen

-swamps

-water-logged soils/muds

-intestinal tracts (guts) of animals

-deep lakes/seas

Oxic Environment

environment that contains oxygen

Categories of Oxygen Requirements (3)

Obligate Aerobes, Obligate Anaerobes, Facultative Anaerobes

Obligate Aerobes

Need continuous supply of oxygen, reside in only oxic environment (all animals/plants)

Obligate Anaerobes

Inhibited or killed by O2, reside only in anoxic environment (methanogenic archaea)

Facultative Anaerobes

uses oxygen when available, can reside in oxic or anoxic environment (E. coli - gut bacterium, Saccharomyces - yeast)

Autotrophs

Make their own carbon compounds from simple substances (CO2)

Photosynthesis

Uses energy from sunlight to fix CO2

Carbon is used to produce carbohydrates, amino acids, and other carbon compounds

Only occurs in eukarya and bacteria, not archaea

Groups that Photosynthesize (3)

-Plants

-Eukaryotic Algae (seaweeds and unicellular algae like chlorella)

-Bacteria (cynobacteria and purple bacteria)

Heterotrophs

Obtain carbon compounds from consumption of other organisms

Digestion, in most, occurs internally after ingestion

*all animals are heterotrophs*

Holozoic Nutrition

Food is swallowed before fully digested

Non-Holozoic Nutrition

Food is digested externally, then ingested (inject digestion enzymes into prey then absorb afterwards)

Stages of Holozoic Nutrition (5)

Ingestion, digestion, absorption, assimilation, egestion

Ingestion

Place food into gut

Digestion

Break large food molecules into smaller ones

Absorption

Transport digested food from inside gut to bloodstream across plasma membrane

Assimilation

use digested food to make macromolecules and incorporate them as part of body's tissues

Egestion

Remove undigested material from end of gut

Family Hominidae

Includes genera like humans (Homo), gorillas (Gorilla), and chimpanzees (Pan)

Some are exclusive herbivores, while others are omnivores

Relationship btwn Diet and Dentition

Studied through examination of skulls, allows for diet of extinct of extinct species to be inferred via dentition

Herbivore Teeth

Tend to be large and flat to grind fibrous plant tissues

Omnivore Teeth

Include a mix of different types, for both meat and plants

-flat molars in back (crush and grind) and sharper canines/incisors than herbivores (tear meat)

Mixotrophic Nutrition

Not exclusively autotrophic or heterotrophic

Facultative Mixotrophs

Either entirely autotrophic or entirely heterotrophic, but can switch between the two

ex. Euglena gracilis photosynthesizes light, but also feeds on detritus/smaller organisms via endocytosis

Obligate Mixotrophs

Rely on both autotrophic and heterotrophic methods of nutrition, cannot survive on just one

ex. some protists lack chloroplasts, so consume algae to steal chloroplasts

-use "klepto-chloroplasts" until they become degraded and need to be replaced

-also consume food for carbon compounds they cannot make

Herbivore Adaptation

Herbivores feed exclusively on plants, have mouthparts evident of adaptation to diet

ex. most insects show great diversity but are homologous (from same ancestor)

Insect Herbivore Mouthpart Adaptations

Either jaw-like mouthparts (beetles) to bite/chew and ingest leaf parts

or

tubular mouthparts (aphids) to pierce leaves or stems, reach phloem and feed on sap

Plant Adaptations to Herbivores (3)

1. Sharp-pointed spines to cause injury

2. Stingers to cause pain

3. Produces toxins

Plant Toxins

secondary metabolites, means not a part of the basic metabolic pathway

stored in any part of plant, usually seeds which are attractive to herbivores bc high [] of protein, starch, or oil

In response to toxins, some herbivores have developed metabolic adaptations for detoxification

Physical Adaptations

Predators: vampire bats have pointed and razor sharp teeth to pierce prey and feed on blood

Prey: Buff-tip moths look like broken twigs to camouflage and avoid predation

Chemical Adaptations

Predators: black mambas produce venom w/ neurotoxins that inhibit acetylcholinesterase to paralyze prey

Prey: Caterpillars of cinnabar moth accumulate toxic alkaloids from ragwort, black and yellow stripes serves as warning coloration

Behavioral Adaptations

Predators: Grizzly bears use ambush strategies to catch migrating salmon, some wait at top of waterfalls while others stick their heads underwater

Prey: Blue-striped snappers swim in tight schools and use sudden changes in direction to confuse predators

Rate of Change in Adaptations

-Behavioral adaptations change relatively quickly (ex blue tits)

-Structural adaptations take longer bc they are based on genetic changes (beak size in finches)

-Chemical adaptations are the slowest bc require new enzymes or regulators processes

Saprotrophic Nutrition

Saprotrophs secrete digestive enzymes into dead organic matter and digest externally b4 absorption (fungi/bacteria)

also known as decomposers

-breaks down carbon compounds in dead organic matter

-releases elements like nitrogen that can be used by other organisms in ecosystem

Plant Adaptations For Light

In environment w/ abundant water and suitable temps. plants compete for light

Forest Ecosystems Diversity for Obtaining Light (5)

Emergent trees, lianas, epiphytes, strangler epiphytes, shade-tolerant shrubs & herbs

Emergent Trees

Dominant leading shoot that grows rapidly, reaches canopy, unshaded by other trees

Lianas

Climb through other trees, using them for support

-no need to produce as much xylem (wood)

Epiphytes

Grow on trunks and branches of trees, access to higher light intensity but also less soil for roots

Strangler Epiphytes

Climb trunks of trees, encircle and outgrow them

-eventually shades out host tree, killing them (and leaving only strangler epiphyte behind)

Shade-Tolerant Shrubs and Herbs

absorb light that reaches forest floor

Fundamental Niche

Potential:

-range of biotic/abiotic conditions that a species tolerate, in absence of competition, entire fundamental niche would be occupied

*adaptations do not allow survival outside range*

Realized Niche

Actual:

-actual extent within fundamental niche that species occupies

-bc competition exists in ecosystems, species are excluded from totality of their potential

*realized niche typically only affects food supply, indirectly affecting species*

Competitive Exclusion

If one species outcompetes the other in all parts of fundamental niche, the outcompeted species (loser) does not have access to a realized niche

-species must have different realized niches to survive in ecosystem

*occurs when fundamental niches of 2 species overlaps, one species usually outcompetes the other*