IGCSE Biology: Biodiversity, Classification, and Adaptations

Comprehensive vocabulary flashcards covering biodiversity, kingdom classification, dichotomous keys, vertebrate and arthropod characteristics, and plant adaptations (xerophytes and hydrophytes) from past exam papers.

DNA Base Sequencing in Classification

The analysis of the specific sequence of bases in an organism's DNA, used by scientists to identify individual people or determine whether a discovered organism belongs to a new species.

Protoctist vs. Prokaryote Cellular Distinctions

Structural differences where protoctists possess a distinct nucleus and membrane-bound organelles (such as mitochondria), whereas prokaryotes lack a nucleus and membrane-bound organelles.

Adaptive Feature

An inherited feature of an organism that helps it to survive and reproduce in its environment.

Cheetah (Acinonyx jubatus) Adaptations

Carnivorous adaptations including fur colouring for camouflage when stalking prey (such as deer and antelope) and a streamlined body shape to increase sprinting speed over short distances.

Xerophytes

Plants adapted to survive in habitats with very little available water, low rainfall, and soils that often have high concentrations of salts.

Water Absorption Adaptations in Xerophytes

Structural and physiological features including long, branching roots to absorb water when it rains and root cells with low water potential so that water moves from the soil into the roots by osmosis.

Water Conservation Adaptations in Xerophytes

Features designed to reduce water loss by transpiration to the atmosphere, including thick cuticles on leaves and stems, as well as few and sunken stomata.

Xerophyte Herbivore Deterrents

Defensive structures such as thin, needle-like leaves (spines) that prevent or reduce herbivores from eating the plant.

Saguaro Cactus (Carnegiea gigantea) Desert Adaptations

Desert survival features consisting of thin, needle-like leaves to reduce surface area, minimise water loss, and deter predators, alongside a thick, fleshy stem adapted to store water.

Part C in Hydrophyte Leaf Cross-Section

Large air spaces within the leaf tissue that provide buoyancy to help the plant float on water and facilitate internal gas exchange.

Hydrophyte Stomatal Distribution

Stomatal arrangement in floating hydrophytes (such as water lilies) where stomata are located on the upper epidermis because only the upper surface is exposed to air, while none are present on the lower submerged epidermis.

Guard Cells

Specialised epidermal cells that flank stomata and control their opening and closing.

Dicotyledonous Plants

A class of flowering plants (such as the orange tree, Citrus sinensis) whose seeds contain two cotyledons.

Exoskeleton

A rigid external body covering present in all arthropods (such as Cerberusa caeca and D. melanogaster) that is absent in vertebrates.

Crustacean vs. Insect Morphological Distinction

Morphological differences that classify an arthropod as a crustacean (such as C. caeca possessing four or more pairs of legs) rather than an insect (such as D. melanogaster possessing three pairs of legs).

Mammalian Diagnostic Features

Characteristics identifying an animal as a mammal, including having fur or hair, presence of external ears (pinnae), lungs for gas exchange, and mammary glands.

Amphibian Features

Distinctive vertebrate characteristics found in amphibians such as frogs, including moist skin and an eardrum (tympanum), lacking scales.