Topic 1, part 2 - Australian flora and fauna

Example species in the Myrtaceae family

Bottlebrushes, tea trees, paperbarks, lillie pillies, eucalypts

Characteristics of Myrtaceae family

Oils in oil glands, Dry fruit or fleshy fruit, regular flower shape

Traits of Myrtaceae flower

Brush-type stigma, oil glands, inferior ovaries, bilaterally symmetrical

Eucalypts are in all habitats except for which 3?

Rainforests, alpine and arid deserts

Which eucalypt is the tallest (maybe 2nd tallest) flowering plant in the world?

Mountain ash

What are the 3 genera in the Eucalypt phylogeny?

Angophora, Corymbia and Eucalyptus

When were the Eucalypt flowers & fruit, and pollen fossils dated to?

30mya and 60mya

Which order are the eucalypt structures arranged in (top to bottom)?

Flower buds, fruits, flowers

Eucalypt flower and fruit development steps

Sepal operculum sheds > petal operculum sheds > Anthesis, stamens displayed and pollen shed > style extends and stigma is receptive > fertilisation  > style withers and ovary swells

Juvenile eucalypt leaves traits

Arranged in pairs, rounded shape, held horizontal, dorsiventral anatomy, sessile

Eucalyptus adult foliage traits

Leaf hangs vertically to reduce transpiration, isobilateral anatomy, 

Types of eucalyptus bark

Rough butt, stringy bark, tessellated, ironbark, smooth bark

What is stomatal aperture controlled by?

The turgor of guard cells determined by the abscisic acid concentration.

Uses for plant water

Turgidity of the plant and as the solvent for reactions in cells. 

How do annuals/ephemerals avoid droughts? Provide a species example.

Spend drier times as seeds and then rapidly grow and reproduce when water is available. Sturt’s desert pea

Why are Mulgas not considered drought avoiders?

They continue to slowly grow and metabolise during droughts

Two major types of Xerophytes (drought tolerators)

Sclerophylls, succulents

Where are the family Ericaceae (epacrids) distributed and what is a distinctive trait?

In heathlands and in low phosphorous soils with bell shaped flowers

What is the name for the “leaves” of Acacias?

Phyllodes - modified stems

4 adaptations of sclerophylls

Small stature, small leaf size (short internodes), proportionally thick leaves, reduced SA:V ratio of leaves

3 anatomical adaptations of schlerophylls

Sunken stomata, thick-walled cells (sclereids fibers and lignin), and thick, waxy cuticles

What is Beadle’s hypothesis?

Sclerophylly first evolved on soils of low nutrient level

What was the rate of advance of the Prickly Pear?

100ha per hour!

Why was the prickly pear so successful?

Waxy, hydrophobic layer around leaves (water tight) and its ability to store water in its stem. 

C3 average gH2O used/gCO2 fixed

400-500

C4 average gH2O used/gCO2 fixed

250-300

CAM average gH2O used/gCO2 fixed

50-100

Why is Rubisco not efficient in C3?

It also catalyses oxygenation of ribulose biphosphate about 20-25% of the time but in high temperatures, up to 40% of the time. Energy wasting.

Benefits of obligate CAM

Plants always perform CAM

CAM idling

Occurs under extreme stress when stomata are ALWAYS closed day and night. No net CO2 uptake 

CAM cycling

Found where water supply is episodic. Stomata don’t open at night , but collect and store CO2 at night and then release it during the day.

Benefits of spatial separation of C4 photosynthesis

CO2 fixed into C4 in mesophyll cells and then transported to bundle sheath cells. Reduces the photorespiration rate due to much higher concentrations of CO2, increasing Rubisco affinity.

How do you differentiate between C3 and C4 by 13/12CO2 levels?

C3 plants have less C13 and C4 plants have more.

What is the Net radiation load made up of?

Solar + heat from surroundings

Sensible heat vs latent heat

Heat you can feel or sense vs the heat absorbed by molecules through heat of vaporisation or heat capacity.

The bigger the difference in the air and leaf temperatures the _____ the sensible heat flux

greater

The smaller the difference in the air and leaf water vapour concentrations, the _____ the latent heat flux

smaller

What is sensible heat loss dependent on?

Thickness of boundary layer and the difference in leaf and air temperature

What is latent heat loss dependent on?

Stomatal aperture and the difference in water vapour concentrations in leaf and air

How do kangaroos reduce radiation load?

Move to the shade

How do kangaroos promote latent heat flux?

By licking their forearms (blood vessels close to the skin)

How do kangaroos promote sensible heat flux?

Dig a hole in the ground to find cooler soil

Diaheliopropism

Leaves always perpendicular to sun’s rays (tracking)

Paraheliotropism

Leaves always parallel to suns rays (avoiding)

How do plants reduce radiation load?

Leaf shape (needle or rolling), reducing leaf amount, Leaf optics

Two general classes of adaptations for surviving fire

Post-fire re-sprouting from buds (dormant buds) and seeding (canopy seed bank or soil seed bank)

Role of phloem

Transports sugars around the plant

Role of cambium

Meristem tissue, actively dividing to produce new cells as plant grows

What is an example species that has lignotubers?

Mallee eucalypt

What did experiments show in regards to smoke and germination?

Species did not germinate at all without exposure to smoke. Smoke was responsible for stimulating germination rates in many species (3-72% germination rate)

What is the carbon molecule that breaks seed dormancy called

Butenolide (by-product of burning cellulose)

Which species are stimulated by smoke that contains ethylene?

Xanthorrhoea and Kingia

Intermediate disturbance hypothesis

Local species diversity is the greatest when disturbance occurs at an intermediate frequency.

Eyrean grasswren physiology to conserve water

Very efficient kidneys, doesn’t drink water, extracts water from dry seeds and small insects

Adaptations of the fat-tailed dunnart

ENERGY CONSERVATION: Eats insects (70% water), low metabolic rate, torpor, fat storage in tail

Adaptations of the Spinifex hopping mouse

WATER CONSERVATION: Seeds (low in water), minimise respiratory water loss, very dry faeces (water reabsorbed in hindgut), super concentrated urine. 

How do Southern Hairy-nose wombats conserve energy?

Low metabolic rates, relatively inactive, avoid high temperatures through being nocturnal.