Evolution of plants Flashcards
(16 cards)
Which adaptations are required for colonisation of land?
- support
- avoiding drying out
- obtaining water
- obtaining gases
- reproduction
- resisting predation
Describe the anthophyte hypothesis
- Bennettitales (extinct group of land plants) suggested to be linked between gnetophytes and angiosperms
- initially based on early molecular data but was more recently challenged with whole-genome sequencing
Approximately how long ago was the evolution of flowers and how old is the earliest fossil?
- approx. 135 mya
- earliest fossil c.125 mya
Describe the key terms for flowering plants
- sepal (calyx) - outer part of the flower. the outside of the flower bud
- petals (corolla)
- stamen (androecium) - the structure in a flower that produces pollen, typically consisting of an anther and a filament
- carpel (gynoecium) - the female structure of a flower composed of an ovary, a style, and a stigma
Describe the significance of the Amborella trichopoda
- small plant native to rainforest of new guinea caledonia
- analysis has shown it is related to all existing flowering plants and belongs to oldest confirmed branch of angiosperm family tree
Describe the predicted structure of the first flower
- probably had petal-like tepals and pollen-bearing stamens
- arranged in layered whorls of 3
- similar to magnolias, buttercups and laurels
- probably had 11 or more tepals and stamen and carried both male and female reproductive structures
List the key trends that occurred in flower structure over evolutionary time
- flowers became generally less complex and more aligned with a common format
- floral structures simplified and flattened from complex spiral arrangements to simpler symmetrical arrangements - tepals divided into petals and sepals and petal fusion occurred
- radial symmetry became less common compared to bilateral symmetry
- carpel tended to be inferior to flower rather than superior
- anther format simplifies
- development of nectaries
Describe the evolution of pollen
- resistant to dessication
- light and easily transferrable
- distinct 3D shape
List the advantages of wind as a pollinator
- can happen at any time
- not reliant on another spp
- can spread long distances
- continuous process
List the disadvantages of wind as a pollinator
- chances of finding target are slim
- requires huge amounts of pollen
- no directionality
- stigma needs to be sticky
- most effective close range
List the advantages of pollenators
- highly efficient
- high volumes of pollen transferred
- large distances
- less pollen required
- more certainty of pollenation
List the disadvantages of pollenators
- costly to produce floral structures
- requires development of complex structures
- seasonal reliance of pollenator
- requires species loyalty
- resource vs benefit
Describe the features of seeds
- a diploid embryo that will germinate into a sporophyte (2n) plant
- storage tissue to sustain growth
- protective coat give seeds their superior evolutionary advantage
- layers of hardened tissue to prevent dessication
- remain in a state of dormancy induced by dessication and hormones until conditions become favourable
How does urbanisation affect plant evolution?
changing conditions and ecosystems require adaptation to changes in plant distribution and pollinator availability
How does climate change affect plant evolution?
Warming environment will need to lead to changes in floral structures, flowering times, species re-adaptation
How does dispersal by humans affect plant evolution
movement of plants and seeds around worlds increases chance of hybrids
