- IB DP Biology 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
- IB DP Biology 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
- IB DP Biology 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 2
- IB DP Biology 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 2
What is a niche?
The role of the species in an ecosystem
-includes: what it eats, when it’s active, its habitat
-includes all biotic & abiotic factors:
1. Biotic: any interaction w/ other living things
-competition, predation, cooperation/mutualism
2. Abiotic: anything that affects its range of tolerance
-temp, air quality
Compare fundamental vs. realized niche.
1. Fundamental niche: potential niche of a species based on its adaptation & tolerance limits
2. Realized niche: actual niche of a species when in competition w/ other species
-Range of tolerance: species have to be able to survive there in the first place
-Population interaction & chi squared: competition between species
Fundamental vs Realized niche – rocky shore data
1. Semibalanus removal:
-Removal of semibalanus barnacles = decrease in Cthalamus barnacle coverage
-Semibalanus affects Cthlamus survival
2. Chthalamus removal:
-removal of chthalamus barnacles doesn’t significantly alter semibalanus barcles coverage
-chthalamus doesn’t affect semibalanus survival
semibalanus is the better competitor against chthalamus
Suggest w/ a reason why chthalamus can survive in high trade, but not in low tide?
Chthalamus has better heat tolerance, able to stand outside in fresh air for longer, and is more resistant to desiccation (drying out). Therefore it can survive in high trade, but not in low tide
Explain the competitive exclusion principle
-One species will always go extinct if two species niches are the same, which leads to interspecific competition
-One species will have an advantage over another
-Less well adapted species will struggle to survive & reproduce, eventually leading to elimination:
1. complete or local extinction
2. population may migrate
What is niche partitioning?
Niche partitioning: small differences in niches that allow for coexisting
-the niches aren’t actually identical, but only look very similar
Compare aerobic vs. anaerobic microorganisms
-Microorganisms = microscopic
-Obligate = mandatory
1. Obligate anaerobe :has to be in a low amount of oxygen, lower than atmospheric
ex: most bacteria in our body, some bacteria in deep ocean/soil
2. Obligate aerobe: has to be in an area w/ atmospheric levels of oxygen
3. Facultative aerobe: can life in either areas w/ or w/o oxygen
Explain photosynthesis
Its is not just performed by plants , but also algae does most of the photosynthesis
-Autotrophs: produce carbon compounds from inorganic compounds using light or inorganic chemical energy
Autotrophs that can do photosynthesis:
1. Algae: huge groups of organisms ranging from seaweed to single celled algae (not a true clade)
2. Plants
-Some aechaeans: prokaryotes & eukaryotes are bacteria & archaeans
-Prokaryotypes – some don’t have a nucleus
Explain holozoic nutrition
Something that eats other things – consumers
-Animals are heterotrophs: obtain carbon compounds from other organic sources
-Holozoic: food is ingested, digested internally, absorbed & assimilated
Explain mixotrophs
May be advantages by allowing for access to more resources
-Can be both autotrophs & heterotrophs: has the ability to do both
-Often protists: single celled eukaryotes
ex: euglena, ocean plankton, different levels
-Can be obligate or facultative – some has to do both autotroph & heterotrophs by using the sun for photosynthesis & eat things ex: venus flytrap
Explain saprotrophs
Recycle nutrients
-Decomposers
-Heterotrophs but not consumers – don’t ingest food
-Secrete enzymes to external environment & digest food externally
-Pull in digested nutrients only
ex: some fungi & bacteria
If saprotrophs didn’t exist to recycle nutrients, then it gets trapped & as many nutrients are needed to grow more crops to support people
Explain archaeans
Archaeans can do multiple different types of nutrition
-One of the 3 domains of life
-Archaeans are extremophiles: like extreme conditions – desert, artic, volcanoes, deep sea, bottom of ocean
-They have 3 main types of nutrition:
1. Light
2. Oxidation of inorganic chemicals (ex sulfur)
3. Oxidation of carbon compounds – eat food
What are different types of plant adaptations for harvesting light?
1. Tall trees – grow tall (canopy or emergent trees)
2. Lianas – root in the ground & then wrap around trees to get higher
3. Epiphytes – grow on other trees; often parasitic
4. Strangler epiphytes – start on trees & then grown down into the ground, taking nutrients from others ex: mistletoe
5. Shade tolerant shrubs – can absorb far red light that can reach the ground through the trees
Explain hominidae teeth
1. Homo sapiens: humans, omnivores – tiny jaw = more space for brain
2. Paranthropus robustus: herbivores – nuts, large premolar & molar teeth, strong lower jaw, ridge on top of skull
3. Homo floresiensis: really small mouth, missing premolars
What are different types of adaptations of herbivores for feeding on plants? Provide example.
Different types of adaptations of herbivores for feeding on plants are:
-Piercing & chewing mouth parts of leaf-eating insects
-Broad, flat molars (back teeth w/ rough surfaces to grind tough plant tissues
-Teeth of most herbivores grow continually
-Specialized bacteria in gut to digest cellulose
Exapmles:
1. Giraffes:
-long neck to reach leaves,
-thick, sticky saliva that coats thorns,
-long, thick prehensile tongue to strap leaves from branches
What are different types of adaptations of plants for resisting herbivory? Provide example
Different types of adaptations of plants for resisting herbivory are:
-Physical barrier: thorns, trichomes, leaf surface wax, cell wall thickness
-Secondary compounds acts as toxins in seeds & leaves
~can affect: growth, development & digestibility reducers
Example:
1. Acacia trees:
-long, sharp thorns
-secondary metabolites as toxins
-ants protects trees
What are different types of adaptations of predators for finding, catching, & killing prey? Provide example.
Different types of adaptations of predators for finding, catching, & killing prey are:
1. Chemical adaptations: venom, toxins, odiferous (bad smell)
2. Physical adaptations:
-long, sharp claws & teeth: tearing
-strong jaws – crush through meat & bone
-special features: long tongue, sharp beaks, webbed feet
3. Behavioral adaptations:
-vision – better at judging distance & seeing small details
-smell – complex nasal passages
-hearing – can swivel ears back & forth
-quick reflex & speed
Example:
1. Tigers:
-long, sharp claws for tearing
-stripes for camouflage
-pads on toes for sneaking
What are different types of adaptations of prey for resisting predators? Provide example
Different types of adaptations of prey for resisting predators are:
1. Chemical adaptations: venom, toxin, odiferous
2. Physical:
-camouflage – blend into surroundings to hide
-shells/spines
-speed – run from predators
-hooves – self defense
3. Behavior:
-vision – all around vision
-hearing – can pick out sound directions
-smell – can smell from great distance
-bluffing – fool predators that they’re dangerous, dead, or hurt