Adaptation 9 Flashcards
What are 5 innovative synapomorphies shown by angiosperms (flowering plants) ?
- Xylem vessels
- Flower
- Carpel & fruit
- Tectate microspore wall
- Double fertilization
Pros and cons of vessel elements? What type of trees would you find in cold/tropical forests?
Vessel elements
- rapid conduction of fluids
- more susceptible to freezing damage
- found in angiosperms, absent from most gymnosperms like conifers
Cold temperature forests
- mostly gymnosperms
- no lianas
Tropical forests
- up to 1/4 species lianas
- exceptionally large vessels
- rapid growth
Describe components of
- Carpel
- Stamen
Stamen ( anther - filament )
Carpel ( Stigma - style - Ovary (ovule) )
What actually is fruit with regards to the components of a plant?
Mature ovary or ovaries
- single carpel = simple ovary, with ovules
- two or more united carpels = compound ovary with ovules
- ovule becomes seed
Structure of ovule (+ megagamentophyte)
- ovule with 2 integuments
- megagametophyte (embryo sac) with 8-nuclei in 7 cells
- 2 synergid cells (= archegonium), 1 egg cell, 2 polar nuclei in one cell, 3 antipodal cells
Describe double fertilisation event. Why is it important?
Unique to angiosperms
- 2 sperm cells released into unfertilised ovule by pollen tube
- one fertilises egg cell (forms diploid zygote)
- one fuses with 2 polar nuclei (forms triploid endosperm)
Seed and fruit now develop
- endosperm provides food supply to zygote once fertilised
- allows faster germination and growth of seedling
- increased survival
What did angiosperms likely originate from? What are the homqologous euivalents for these terms?
- nucellus
- embryo-sac
- synergid cells
- inner integument
- outer integument
- carpel
- stamen
- petal
- sepal
Progenitors probably Mesozoic seed-ferns, e.g. Caytonia
- reticulate leaf venation (resembles a network)
- nucellus = megasporangium
- embryo-sac = megagametophyte
- synergid cells = archegonium
- inner integument = integument
- outer integument = seed-fern cupule
- carpel = bract subtending seed-fern cupule
• stamen = seed-fern branch with
microsporangia
• petal = sterile stamen (usually)
• sepal = modified bract or leaf
Main reasons for angiosperm success?
• close relationship with animals (co-evolution)
- pollination (by animals in most cases)
- fruit dispersal (by animals in some cases)
- biochemical defences against herbivores
• self-incompatibility
What are the adaptive significances of biotic pollination? What do they lead to?
- pollen transfer more efficient than by wind
- fewer pollen grains needed
- provides another mechanism for reproductive isolation
- promotes speciation
Leads to
- Co-evolution of flowers and animals, especially insects
- Mutualism: positive feedback system, based on reciprocal rewards (food, or shelter (flower basking)) in exchange for pollination
- Biotic pollination syndromes, i.e. the association of a particular combination of floral features with an animal or group of animals
What compounds are responsible for the colours of fruit and flowers?
- Flavonoids, incl. anthocyanins: water-soluble, phenolic componds in vacuole (red, yellow, blue)
- Carotenoids: oil-soluble, (yellow)
Characteristics of beetles in pollination process
- how are flowers associated with beetle pollination typically adapted?
Beetles
- poor eyesight
- good sense of smell
- feed on pollen & other flower parts, sometimes nectar
Flowers
- white or dull in colour
- have a fruity or fermenting odour
- ovules usually located away from the zone where beetles feed
Characteristics of bees in pollination process + flowers
Bees
- most important group of flower-visiting insects
- feed on nectar
- females collect pollen for larvae
- specialised mouthparts, body hairs, etc.
- highly developed sense of pattern recognition: flower fidelity high
Bees see yellow, blue & UV but cannot easily distinguish red from green part of e-m spectrum
Characteristics of butterflies in pollination process + flowers
Butterflies
- Feed on nectar
- Some butterflies can see red
Flowers
- Like bee-flowers but often orange or red
- Often have long corolla tubes
Characteristics of moths in pollination process + flowers
Moths
- most moths are nocturnal
- feed on nectar
Flowers
- white or pale
- have a heavy scent, often emitted only after sunset
- have a nectary in a spur or at end of long corolla tube accessible only to long proboscis e.g. Yucca
Characteristics of birds in pollination process + flowers
Birds
- humming birds – New World
- sun birds – Old World
- vision similar to humans
- poor sense of smell
- feed on nectar, flower parts & flower insects
Flowers
- colourful, especially red or yellow
- have little or no scent
- have copious, viscous liquid nectar
e. g. Fuchsia, Hibiscus, Passiflora
