SCIN Biology Unit (SHORT DEFINITIONS ONLY)

Biology unit terms and definitions for investigative science, this set contains only shorter answer questions

Xylem

dead, hollow, long thin tubes which allow water to move up the stem from the roots to the leaves. They have specially thickened cell walls which hold the plant up.

Capillary action

adhesion and cohesion of water molecules.

Phloem

living, long tube like cells which carry glucose down the stem from the leaves to the roots. Small holes in the ends of the cells allow the continuous flow of glucose between cells.

Cambium cells

where cell division, mitosis, occurs in the stem of plants, making more xylem and phloem cells

Vascular bundles

consists of xylem, phloem, and cambium

Osmosis

the movement of water from high concentration to low concentration through a semipermeable membrane

Turgid

when plant cells are stiff and full of water, holding up the plant upright.

Flaccid

when plant cells are dehydrated and the plant wilts

Hypertonic solution

a solution with a high concentration of solute dissolved in water

Hypotonic solution

a solution with a low concentration of solute dissolved in water

Isotonic solution

a solution with the same solute concentration inside and outside the cell

Transpiration

the evaporation of water from the surface of leaves

Transpiration pull

the pull of water up the xylem of the plant when water evaporates from the leaves

Waxy cuticle

a waxy layer preventing evaporative water loss

Epidermis

protects palisade mesophyll, helps to prevent water loss, single transparent layer permits light to pass into the leaf

Palisade mesophyll

tightly packed layer of cells with large amounts of chlorophyll for absorbing sunlight, main site of photosynthesis.

Spongy mesophyll

irregular in shape and loosely packed, fewer chlorophyll and large air spaces for exchange of CO2 and O2 gases between leaf palisade layer and environment.

Stomata

Small holes in lower surface controlling gas exchange and rate of transpiration

Guard cells

Swells or shrinks with water by osmosis to control the opening or closing of Stomata

Turgor pressure

water pressure

Conditions for photosynthesis

sunlight and chlorophyll

Site for photosynthesis

chloroplast

Purpose of photosynthesis

to make food from sunlight

Airspaces

speeds up the rate of diffusion

Labelling parts of the cell (from top to down, left side then right side)

Nucleus, cytoplasm, cell membrane, mitochondria, cell wall, vacuole, chloroplasts

Labelling parts of the leaf (from top to down, left side then right side)

Blade, midrib, vein

Labelling cross section of the leaf (top to bottom)

Waxy cuticle, upper epidermis, palisade mesophyll cells, spongy mesophyll cells, xylem, phloem, lower epidermis, stoma

Factors that increase the rate of transpiration

high wind, high light intensity, high temperature, low humidity

Meristematic tissue

The tissue in plants where cell division takes place

Primary growth

the elongation of the plant, the plant growing taller

Name the 2 processes that occur in primary growth

1. cell division/mitosis in the zone of cell division (meristem) 2. cell elongation in the zone of cell elongation

Secondary growth

the increase in diameter/thickness of roots/stems/branches

Where does secondary growth occur?

cambium

Cambium

made up of meristematic cells that are undifferentiated, found between the xylem and phloem in vascular bundles

Meristematic cells

cells that undergo mitosis

First stage of secondary growth in the stem

Cambium in vascular bundles grows completely around the stem to form a ring and the cambium thickens

Primary xylem and phloem

another term for old phloem and xylem

Why do trees form rings?

In summer the xylem cells grow larger than in winter, forming rings of larger, lighter wood, and smaller, darker wood

Why is secondary growth important to the development of the plant?

1.thickening of the stem can support a larger and taller canopy, capturing more light for the plant 2. more xylem and phloem is created, therefore more sugar and water can be transported to the increased amount of plant tissue.

Functions of the root

Anchor the plant into the soil, absorb water and minerals, store food in the form of starch

Parts of the root

Root cap, meristematic tissue (zone of cell division), zone of elongation, zone of differentiation, root hairs

Root cap

produces a layer of slime that coats the surface of the root and lubricates it as it pushes through the soil

Zone of elongation

the cells get longer

Zone of cell differentiation

the cells start to become specialised for a specific function

Root hairs

increase the surface area available to absorb more water and minerals from soil

Tropism

a growth response of a plant towards or away from a stimulus coming from one direction

Types of tropisms

photo, geo, hydro, chemo, thermo, thigmo

Phototropism

light

Geotropism

gravity

Hydrotropism

water

Chemotropism

chemical

Thermotropism

heat

Thigmotropism

touch

Where is auxin produced?

in the shoot tip (apical meristem) of the shoots, ie the zone of cell division and the meristematic tissue. Auxin travels down into the zone of elongation

What does auxin promote?

promotes the elongation of cells in the zone of elongation, therefore increasing upwards growth

Where does auxin migrate to?

in shoots, auxin migrates to the dark side of the zone of cell division then flows down into the dark side of the zone of elongation

Where does auxin accumulate?

auxin accumulates in the lower side of the stem or root due to gravity

High auxin concentration in stems

causes cell elongation to occur

High auxin concentration in roots

inhibits cell elongation

Auxin in the root cap was originally produced…

in the youngest leaves and transported to the root via the phloem