Plant Evolution (Block 6) Flashcards
What were the first instances of herbivory centred around in evolutionary history?
Eating dead plant material.
What was probably the first producer on land before land plants?
Algae, forming algal mats.
What were the earliest food chains on land based on?
Detritovores//algae-eaters, which ate algae and were likely eaten by other animals.
Why are bitten leaves not enough energy for herbivory?
The leaf could already be dead.
What is good evidence for herbivory?
A bitten leaf with a healing response (meaning it is alive).
How did detritivores make the change to herbivory?
Leaves decay gradually, so arthropods gradually evolved to eat leaves that were less and less dead over time.
How did carnivorous animals make the change to herbivory?
They started by eating the occasional plant, and gradually making the switch to omnivores, then carnivores.
How long did it take for herbivores to evolve after the first land vertibrates evolved?
95 million years.
Why was it difficult to evolve herbivory?
> Cellulose is hard to digest.
> Plant chemical defences.
Why might flight have evolved in animals?
> To reach PLANT food.
> To evade predators.
How may the evolution of flight involved plants?
Flight first evolved by launching from a high place and trees provided this height.
Why would animals launch themselves from trees?
> Gravity gets you down faster after climbing.
What benefits would plants get from animals climbing them?
Insects may have dispersed spores by eating them like modern birds disperse seeds.
How did spore consumption by insects aid the seedless vascular plant life cycle?
Usually, sperm from one plant has to swim to another, but an insect could excrete 2 or more plants together, enabling breeding.
How did grass take over?
> Grass has lower growing points, so if it is grazed it will grow back, unlike monocots.
Grass has a uniform silica defence, which grazers can adapt to, whereas monocots have varied chemical defences.
When is C4 photosynthesis most advantageous?
Photorespiration-favouring conditions.
What conditions favour photorespiration?
Hotter, drier climates, and low CO2.
How can C4 evolution be traced with C isotopes?
C4 system has a WEAK bias against C(13), and takes it in fairly easily, but C3 has a STRONG bias and RuBisCO gets rid of C(13). Isotope ration in fossils can tell if a plant was C3 or C4, even if it is the fossil of an animal that ate it.
How is an F1 hybrid different from the common ancestor of its parents?
Evolutionary Novelty - It contains genes that evolved after the ancestor, never seen in a plant together before.
What 4 things can happen following a hybrid swarm?
> Nothing
Introgression
New species evolves
Rarer parent goes extinct
What is most likely to happen to a hybrid swarm?
Nothing: it persists but no special outcomes occur.
Why is Geographical Isolation (1) a barrier? How can it be broken?
> Distance prevents pollen transfer.
> Broken by human introduction
Why does transgressive segregation occur?
The mix of alleles inherited by the F2 hybrids is very random, as is recombination.
What is transgressive segregation?
When F2 hybrids have unpredictable phenotypes, which can be extreme relative to the parents.
What effect can habitat disruption have?
Makes novel ecological conditions, and it can make an intermediate habitat (good for hybrids).
What is special about the habitat requirements of F2 hybrids?
Their optimum habitats are unique and can vary from that of the parents.
What is extreme segregation?
When complex hybrids (after F2) are actially suited so habitats which are toxic to the parents.
Give an example of extreme segregation.
Sandy-soil H. annus & Clay-soil H. petiolaris crossed to produce F6 hybrids, where some are suited to very dry habitats and some to saltmarshes.
What is introgression?
Gene transfer by hybridisation (natural GM) by repeated backcrossing of a hybrid with one of its parents.
Give an example of introgression.
S. squalidus (Northern) x S. vulgaris (Mediterranean) hybrid backcrossed repeatedly with S. vulgaris. The resulting individuals look like S. vulgaris with small ray florets and winter dormancy.
What does Wu’s Genetic Species Concept describe?
Some DNA flows freely between species, BUT the genes that make species different DO NOT.
