Evolution and Biogeography of Australian Flora Flashcards
plants arose from
an algae like ancestor
bryophytes
earliest branching, oldest plants
- liverworts, mosses, hornworts
- use spores not seeds
- lack vascular tissue (small)
pteridophyte
oldest vascular plants
- lycophytes, ferns and horsetails
- use spores but height helps with dispersal
gymnosperms
oldest seed producing plants (naked seeds)
- pines, conifers
- pollen and seeds by cones (sexual organs)
angiosperms
most recent and common (enclosed seeds)
- 90% land plants
- flowers and fruit aid pollenation
- sexual selection
why are there similar species in southern areas?
past connections and continental drift
australia in Gondwana
- cretaceous and cenozoic: Australia was part of Gondwana (NZ, South America, Africa etc.)
- Australia left Antarctica 30 mill yr ago
- isolation and evolution
eucalypts facts
75% of biomass
700 species, most endemic to Australia
break up of Gondwana and eucalypts
160mya
- Australia, Antarctica, South America and NZ were connected
- eucalyptus ancestors in wet rainforests
- eucalyptus pollen 100-66mya (cretaceous)
- monsoonal (not many fossils) climate, volcanic activity and bushfires - oils make fires easy to start but hard to maintain
where did eucalyptus go in NZ, South America etc.
- need fire to regenerate
- wet conditions = fungi, bacteria, disease
- too wet in NZ
arrival of humans
arrived 50 000 years ago from Indonesia and china
charcoal evidence suggests earlier
extinctions
terrestrial environments
tropical, subtropical, temperate, warm temperate
- great divide - wetter on the East (rainforests) and frier on the west (dry woodland)
- deserts in central australia
El Nino - Southern Oscillation
2-3 year cycle
usually warm aid goes west to east (cools and descends) high pressure zone
air in the east warms during EN and low pressure in east - drought and bushfire
la nina
above average rainfall and flooding
el nino and la niña are enhanced by
climate change
marine environments
pacific, southern and Indian oceans
latitude and structure of continental shelf affects environments
relic and major components of Australian flora
relic live in moist, rainforests
major has adapted to arid conditions
dominance of hard leaves
sclerophylls
- survive with low nutrients, water stress and fires
- short leaves, thick cuticle and sunken stomata
succulents
- store water in leaves and stems
- xerophytes (live in dry conditions)
- sunken stomata
myrtaceae
eucalyptus family. 4-5 perianth parts and numerous stamens
proteaceae
banks family - 4 lobed perianth, 4 stamen
ericaceae
heath family - stiff leaves and tube like flowers, infertile soils
mimosaceae
wattles - 1000 species, increase nitrogen content of soils
fabaceae
pea family
asteraceae
daisy family
orchidaceae
orchids
northern plants
migration of plants from elsewhere into the north
seeds in tufts or hairs disperse
how to flowers spread pollen
attracting animals to flowers and fruit
stamen
male reproductive parts
filament: holds anther away from flower for pollinators to access
anther: contains pollen grains (each has two sperm cells)
sepal
modified leaves that surround the bud. make up perianth that envelops the reproductive parts
petals
modified leaves that also make up perianth
- colours attract pollinators
pistil
female reproductive part. pollen lands on the sigma and germinates, sending a pollen tube containing sperm down the style. pollen tube delivers sperm to the ovary (egg in an ovule)
inflorescence
arrangement of flowers like with banksia
can support birds
lots of nectar
indigenous use of plants
medicine insect repellent dye transport fire have multiple uses
