Evolution of Australian Biota Flashcards
natural selection:
- evolution is NOT random
- mutations ARE
- natural selection is the environment which chooses the most beneficial/suited mutation for environement
biota:
living things
marsupials found:
south America, New Guinea, Australia
evidence that Australia was part of ancient super continent Gondwana:
matching continental margins;
- fit together like jigsaw
- theory of plate tectonics: continental and ocean basins overlapping and moving through time
position of mid ocean
- form boundaries of earth’s crustal plate
- plates move apart as lava in added to ridges,
- sea floor spreading occurs where two crustal plate move apart, rock increases with age: more evidence
common fossils on Gondwana continents
- Glossopteris and Gangamopteris are distinctive plants from Permian Age, found only in Australia, India, Antarctica and New Zealand
Similarities between present day organisms:
- plants: floras of southern continents have many common features (eg. Myrtaceae family: eucalyptus)
- animals: flightless birds in each continent are believed to have descended from a common ancestor
example of australian fauna: and similarities to modern equivalent
Dromornis:
- thought to be like emu, cassowary: large flightless bird
- but now believed similar to duck/geese
Continental drift idea:
- super-continent Pangaea
- but due to continental plate activity, continents drifted apart
- fossil symbols and mountain belts help in moving continents to og
- current position too separate to have similarities
- proves theory of og super-continent
- present shapes don’t match exactly because of new rock and land forms, erosion
- most occurring fossil: Glossopteris plant,
Gondwana includes:
- South America
- Africa
- India
- Antarctica
- Australia
Theory of natural selection:
- the environment selects favourable traits/variations in species and eliminates harmful ones
- over generations, best traits evolve to be common, and population adapts to their environement
- proposed by Darwin and Wallace
Darwin’s theory of natural selection:
- any population have variations
- organisms that survive and reproduce are well adapted to their environment, with favourable variations (survival of the fittest)
examples of species variation and where it came from
- cows, dogs, flowers and plants
- the more variations, the better the species can survive
variations are from:
- modern genetics
- recombination of genes in sexual reproduction
- by chance
- variations may not be advantageous until change in environment (black peppered moths –> black bark beech trees)
- usually animals in cool, southern areas are larger than same species –> smaller surface area:volume, retain heat
- colour variations
- variation in height, size, thickness > with altitude (eg. snow gum)
evidence of changed environments in Australia:
fossil evidence:
- sedimentary rocks, most common rock in Aus,
- contain evidence (fossils) to vast changes in distribution and abundance of species, due to environmental changes over millions of years
eg. limestone areas (Jenolan, Wombeyan) were once covered in warm shallow oceans, containing numerous corals/molluscs/fish
eg. fossils of Thylacine were found in Kimberly
areas in Australia experiencing significant variations in temperature and availability
environment:
- drifted north from Antarctica, creating warmer/acid
- vast rainforests gave way to small coastal ones and inland deserts
- sclerophyll (hard-leaved) forests now dominate
- central Aus. experience large temperature variations, max in summer, min in winter
changes in Australian Flora and Fauna: Distribution of species/adaptive radiation
- Australia became warmer/drier, plants and animals evolved to survive increasing aridity
adaptive radiation
- change of species from og form to different from adapted to different environment and ways of life
changes in Australian Flora and Fauna: vegetation changes
- rainforest declined, Australia dominated by acacias and eucalypts
- evolved to survive hot/dry conditions
eg. common black wattle, swamp mahognany
changes in Australian Flora and Fauna: animal change
- fossil record indicates placental mammals died out, marsupials survived and thrived, diversified
- eg. Australian frogs learned to cope with temporary sources of water
Current theories providing model for changes:
The theory of evolution by means of natural selection:
Hypotheses:
- based off fossil record in Riversleigh (NW QLD), Narcoote in SA
- fossil eviedence show 2 main factors of change:
Charles Darwins’ observations of Australias’ flora/fauna, relating to his theory of evolution:
- landed in sydney, 1836
- observed uniqueness of Aussie Biota, but also had similarities to world, which were unrelated (eg. marsupials and placental mammals: rabbit, hare, wallaby)
- similar niches and ways of life, resemble physiologically and structurally
- all from common ancestor
way evolution is controversial:
- religion
- missing links
- no thorough understanding
- Huxley and Wilberforce (first debate) 1860\
- Scopes “Monkey” Trial 1924
- Dover Intelligence Design Trial 2004
sample of Australian fossil and modern equivalent, structural adaptation:
- Obdurodon insignis (Cenozoic period)
- similar to platypus
- tooth like baby platypus
- yet, they kept teeth: 1m long
- double modern size, more elongated snout and straighter
factors causing extinction eg:
Thylacine:
- out competed with dingoes and introduced dogs, human hunting pressure
Flower parts: male/female
men- stamen:
- anther
- filament
female- carpel/pistil
- stigma
- style
- ovary
- ovule
self-pollination/cross pollination
self:
- transfer of pollen in same flower
cross:
- from pollen of plant 1 –> stigma of plant 2
- same species
adaptations for cross-pollinating plants:
eg. banksia (bottle brush)
- stigma and pollen inside ‘brush’
- possum must brush past hooks (stamen) to pollinate stigma
adaptations for self-pollinating plants:
eg. pea plant
- pistil and anthers are within easy reach to poillinate itself
Meiosis:
- where Eukaryotic cells contain 1/2 no. of chromosomes in preparation of reproduction, called a ‘gamete’ cell
- after fertilisation, two gametes produce og no. of chromosomes to offspring
Haploid and Dipoloid:
Diploid
- most somatic cells contain certain no. of chromosomes called diploid no. 2n
Haploid:
- gamete cells,
- contain 1/2 of diploid chromosomes: n
zygote:
- where two haploid cells fertilise and combine into new diploid cell
- contains both genes of male and female gamete cells
Meiosis process:
- occurs only in diploid/polyploid cells
- replicate chromosomes once –> divide twice
- 1 mother cell –> 4 daughter cells
- all randomised/new combinations
- none similar to original mother cell
chromatid:
two sister (same) or non sister (different) chromosomes connected by centromere
homologous pair:
where one maternal chromosome matches with a paternal chromosome
chiasma:
crossing over of homologous chromosomes, where parts of chromosomes break off and recombine with different chromosome
external fertilisation:
- takes place outside the body
- common in most aquatic organisms
- water used as medium to fertilise successfully
- millions of gametes released to overcome predation and low survival
- mating rituals help simultaneous release of sperm and eggs
internal fertilisation:
- occurs inside body
- land organisms face problem of gamete/zygote drying out
- therefore in body is more stable, moist
- internal transfer of gametes in controlled environment
- animals developped a penis to successfully transfer into female
- pollen tubes for plants prevent drying and transfer to ovaries
asexual reproduction advantages/disadvantages: and examples
advantages:
- when conditions are stable and favourable ofr organism, asexual reproduction is advantage
- allows large numbers of offspring be reproduced rapidly
- only one parent needed
- ESPECIALLY if organism is ‘sessile’ (immobile), no need for mate
disadvantage:
- in changing environment, asexual reproduction produces little variation (only own genes)
eg: colony wattle:
- shoots from outer roots
- grow into separate plant
- if parent plant dies/burned, seed reserves destroyed is ok
eg. coral
- reproduce quickly by ‘budding’
sexual reproduction
- done through pollination
eg. bearded ochid:
- pseudo copulation, flower looks like female wasp
- cross pollinate
Seed dispersal:
- main dispersal stage for flowering plants
- can be alone, in fruit (by animals), wind and water
- eg. Aussie ants play vital role in this seed dispersal
- Wattles and Pea plants have special outgrowths where ants eat the take seed away to nest
- Banksia have winged seeds to aid dispersal by wind
