IB Biology SL B4.2 Ecological Niches Questions

Practise IB Biology SL B4.2 by comparing niches, habitats, resource use, nutrition and environmental requirements with evidence.

Exam points

Define an ecological niche as a species’ role, then compare species by habitat, resources and biotic or abiotic interactions.
Identify oxygen availability as a survival requirement for obligate aerobes in an environmental scenario.
Distinguish autotrophic from heterotrophic nutrition and explain how photosynthetic prokaryotes released oxygen into the early atmosphere.
Identify holozoic nutrition from ingestion and internal digestion, including evidence that distinguishes it from external saprotrophic digestion.
Classify Euglena or other named protists as mixotrophs when evidence shows both photosynthesis and heterotrophic feeding.
Identify fungi or bacteria as saprotrophs in food-web evidence, and explain external digestion, decomposition and nutrient recycling.
Identify methanogens as methane-producing Archaea and relate them to anaerobic conditions or habitats; identify halophile habitats from salt evidence.
Compare tooth-count, jaw and molar evidence across named Hominidae fossils, then relate dentition trends to dietary change.
Identify herbivore feeding adaptations such as chewing mouthparts, grinding teeth, long guts or cellulase-producing microbes.
Explain how prey camouflage, chemical mimicry or shell armour—and predator or prey morphology—change detection, attack or predation success.
Interpret chlorophyll and leaf-nitrogen data across light conditions, and explain how greater leaf chlorophyll supports light harvesting in low light.
Distinguish fundamental from realized niches and use interaction evidence to explain why a species occupies a narrower range.
Explain competitive exclusion and interpret Paramecium or other niche-overlap data to identify which species is excluded or restricted.

Covered syllabus points

B4.2.1—Ecological niche B4.2.2—Oxygen tolerance B4.2.3—Photosynthesis as nutrition mode B4.2.4—Holozoic nutrition B4.2.5—Mixotrophic nutrition B4.2.6—Saprotrophic nutrition B4.2.7—Diversity in archaea B4.2.8—Dentition and diet in Family Hominidae B4.2.9—Herbivore and plant adaptations B4.2.10—Predator and prey adaptations B4.2.11—Plant form for light harvesting B4.2.12—Fundamental vs. realized niche B4.2.13—Competitive exclusion

[Maximum number: 6]

Ecologists studied the distribution of five species of insectivorous wood warblers of the genus Dendorica living on different parts of coniferous trees in mature forests.

(a)

Outline the principle of competitive exclusion

[ 2 ]

(b)

Other than position in the tree, suggest two ways in which the niches of the warblers in the ecosystem may differ.
1:
2:

[ 2 ]

(c)

The diagram shows the realized niches of the five species of warbler. Suggest how the fundamental niche of D. castanea might differ from its realized niche.

[ 2 ]

[Maximum number: 1]

A student set up a 20 -metre transect line along a rocky shore and measured the abundance of seven species of seaweeds (A-G) at 21 different sampling stations at fixed distances. The kite diagram represents the species abundance data across the 20 metres.

Seaweeds are obligate aerobes. Describe an environmental condition required for seaweed survival.

[Maximum number: 3]

There is evidence that prokaryotes were responsible for changes in the atmospheric gases 3.5 billion years ago. Outline the role of bacteria in producing an oxygen-rich atmosphere.

[Maximum number: 2]

Ecologists studied the distribution of five species of insectivorous wood warblers of the genus Dendorica living on different parts of coniferous trees in mature forests.

Other than position in the tree, suggest two ways in which the niches of the warblers in the ecosystem may differ.
1:
2:

[Maximum number: 1]

What describes holozoic nutrition?

Nutrition type

Digestion

chemoautotrophic

none

photoautotrophic

none

saprotrophic

external

heterotrophic

internal

[Maximum number: 1]

Psammonobiotus balticus belongs to a group of protists (unicellular eukaryotic organisms) that have a shell surrounding most of the cell, which provides shelter from predators. The graph shows the frequency of varying shell lengths in a population of P. balticus.

Outline the reason that some species of protists are classified as mixotrophs.

[Maximum number: 1]

What is a difference between detritivores and saprotrophs?

Detritivores

Saprotrophs

Feed on living organic matter

Feed on dead organic matter

Autotrophic

Heterotrophic

Ingest organic matter and then digest it

Digest organic matter and then absorb it

Include fungi and bacteria

Include plants and animals

[Maximum number: 1]

Which organisms produce methane in anaerobic environments such as waterlogged soils?

Archaea

Fungi

Eukaryotes

Eubacteria

[Maximum number: 3]

Scientists examined the teeth of a group of related species of cichlid fishes in Lake Tanganyika, Africa, to determine their evolutionary relationship. The group contains six species from two genera, Perissodus and Haplotaxodon. The chart shows the number of teeth per jaw of these species and indicates whether each is adapted to feed in shallow water or deep water. Species from the genus Perissodus are known for their unique feeding habit of eating the scales of other fish.

Horizontal point-and-error-bar chart of teeth per jaw for six Perissodus and Haplotaxodon fish species. Open and filled circles distinguish upper and lower jaws; a side strip indicates shallow- or deep-water adaptation.

Key: ○ upper jaw • lower jaw □ shallow water ! deep water

(a)

State the mean number of teeth on the upper jaw of P. straeleni.

[ 1 ]

(b)

Compare the teeth on the upper and lower jaw of P. elaviae and P. hecqui.

[ 2 ]

[Maximum number: 4]

Convergent evolution increases similarities, despite differences in origins.

Suggest examples of adaptations in herbivores for feeding on plants.

[Maximum number: 3]

Butterflies have evolved different methods of defence against bird attacks. The relative escaping ability and unpalatability (distastefulness) of different tropical butterfly families and subfamilies was investigated in the presence of wild kingbirds, Tyrannus melancholicus, a natural predator of butterflies. Each symbol on the graph represents a different species within a (sub)family.

Greater ability to escape

Lesser ability to escape

(a)

Suggest one feature of butterfly wings that might help a butterfly to escape from a predator.

[ 1 ]

(b)

The graph shows that distasteful butterflies tend to have a lower ability to escape from predators than palatable butterflies. Suggest reasons for this trend.

[ 2 ]

[Maximum number: 6]

The nitrogen content of a leaf is mainly due to the proteins contained in the chloroplasts. These proteins are either in the thylakoids or in the stroma, where most enzymes are found. The quantity of nitrogen from the thylakoids is directly proportional to the amount of chlorophyll; a ratio of approximately 50 mmol nitrogen : 1 mmol chlorophyll would represent 100 % of the leaf nitrogen content. Scientists hypothesized that the higher leaf percentage nitrogen content resulting from a decrease in light intensity is due mainly to an increase in chlorophyll in many plant species, three of which are represented in the following graph.

Plot of leaf chlorophyll content against total leaf nitrogen, both in mmol m⁻², with an angled scale for nitrogen in chlorophyll as a percentage of total nitrogen. Squares, circles and triangles denote Alocasia, Spinacia and Phaseolus; open and filled symbols distinguish low and high light.

(a)

State the difference in chlorophyll content for Phaseolus between high and low light intensity, giving the units.

[ 1 ]

$0.08 \mathrm{mmol} \mathrm{m} \mathrm{m}^{-2}$ (Accept answers between 0.07 and $0.09 \mathrm{mmol} \mathrm{m} \mathrm{m}^{-2}$ . Units required.)

(b)

State the percentage value of total leaf nitrogen in chlorophyll for Spinacia at low light intensity.

[ 1 ]

(c)

Suggest one advantage for plants to increase their leaf chlorophyll content per surface area when light intensity is lower.

[ 1 ]

(d)

Evaluate the hypothesis that lower light intensity increases thylakoid nitrogen.

[ 3 ]

[Maximum number: 2]

Ecologists studied the distribution of five species of insectivorous wood warblers of the genus Dendorica living on different parts of coniferous trees in mature forests.

The diagram shows the realized niches of the five species of warbler. Suggest how the fundamental niche of D. castanea might differ from its realized niche.

[Maximum number: 2]

Ecologists studied the distribution of five species of insectivorous wood warblers of the genus Dendorica living on different parts of coniferous trees in mature forests.

Outline the principle of competitive exclusion

All question bank results loaded

a	different food/prey;
b	different predators;
c	active at different times of the day;
d	present at different times of the year;
e	different nest sites;
f	different temperatures;

a	different food/prey;
b	different predators;
c	active at different times of the day;
d	present at different times of the year;
e	different nest sites;
f	different temperatures;

a	no two species can occupy the same niche;
b	competition between them would cause one species to drive the other out OR one of the two species would need to adapt and evolve accordingly;

a	the realized is the actual niche and the fundamental is in the absence of competition;
b	with no competition D. castanea would have a larger habitat/more food OR D. castanea could occupy the niches currently occupied by the other warbler species;

Covered syllabus points

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