ENVIRONMENTS

Read 199-207

SIZES OF ENVIRONMENTS

SMALLEST

LARGEST

• ORGANISM• MICRO-HABITAT• HABITAT• BIOME• BIOGRAPHICAL REGION• BIOSPHERE

ECOSYSTEMS

• BIOTIC – living• ABIOTIC – (A)non-living• Examples:

• Abiotic factors that influence tolerance (worksheet)

BIOTIC ABIOTIC

COMPARISONSFACTORS AQUATIC HABITAT TERRESTRIAL HABITAT

Water availability

Dissolved minerals

Temperature

Light

Buoyancy/Density

Viscosity (resistence to movement)

Gas availability

Pressure

COMPARISONSFACTORS AQUATIC HABITAT TERRESTRIAL HABITAT

Water availability Readily available Varies in availabilitySpecies have special features to transport it

Dissolved minerals Ions in waterFresh water – low soluteSalt water – high solute

Ions in soilVariable in amounts

Temperature Less variation Greater variation

Light Limited – depends on clarity Readily available

Buoyancy/Density More dense = more support Less dense = less support

Viscosity (resistence to movement)

Very viscose Not very viscose

Gas availability O2 not readily availableCO2 readily available

O2 readily availableCO2 not readily available

Pressure Increases with depth Descreases with altitude

ECOLOGICAL NICHE

• An ecological niche describes how an organism or population responds to the distribution of resources and competitors . The way of life of a species.

• The optimum range refers to the abiotic factors at which the organisms functions best.

• Physiological stress refers to outside the preferred niche/optimum range.

• Looking at niches (worksheet)

PLANTS & TROPISMS

Read 219-228

TROPISMS

• Tropism is the directional growth response of a plant to an environmental stimulus.

• Positive tropism – growing toward a stimulus• Negative tropism – growing away from a

stimulus• Complete the table:

Tropism Stimulus Response

Phototropism

Geotropism

Hydrotropism

Thigmotropism

Chemotropism

TROPISMS

• Tropisms (worksheet)• Leaves can tell a story (worksheet)

Tropism Stimulus Response

Phototropism Light Positive: shoots grow towards the lightNegative: roots (if responsive) grow awy

Geotropism Gravity Positive: roots grow downwardsNegative: shoots grow upwards

Hydrotropism Water Roots grow towards water

Thigmotropism Touch, contact Stems and tendrils grow round or against points of contact with solid objects (eg other plants)

Chemotropism Chemicals Positive: pollen tubes of some plants are attracted to the stigma of same species, enabling fertilisation. Ovary releases chemicals to produce response.

PLANTS IN DEFFERENT ENVIRONMENTSCategory Description Characteristics

Hydrophytes Aquatic plants: floating or living in water

Have little or no cuticle on stems and leaves. Stomata (specialised pores for gas exchange) are found on the upper surface of the leaves. Small amount of transport tissue (xylem).

Xerophytes Dry conditions Fleshy, succulent plants OR hard-leaved sclerophylls. Thick waxy cuticle, hair covering leaves, few stomata, reduced leaf surface area, leaf orientation away from sun.

Halophytes Salt tolerant Many are succulents. Usually have high osmotic pressure in cytoplasm, control salt levels in shoots. If excess salt enters via the leaves they cannot control osmotic concentration so stomata close reducing transpiration and CO2 uptake.

Mesophytes Moist conditions Perennials – survive underground as bulbs, tubers. Annuals survive with dormant seeds. Stomata control water loss.

Epiphytes Aerial: growing on branches or trunks.

Not parasitic.

Which is which?

Know the definitions of these:• Epicormic bud• Lignotubers• Phytohormones• Gibberellins• Cytokinins• Abscisic acid• Ethylene• Auxins

• Life of Plants (video)

• Phytochromes• Photoperiodism• Dormancy• Taxis• Nastic• Nutation