Phenotypic plasticity

Question 1

What is phenotypic plasticity?

Answer 1

The production of multiple phenotypes from a single genotype, depending on environmental conditions in response to biotic and abiotic aspects of their environments
Encompasses all types of environmentally induced changes (morphological, physiological, behavioural, phenological)
Plastic responses can be expressed within a lifetime of individual or across generations

Question 2

What are the three mechanisms that swtich on/off genes in epigenetics?

Answer 2

Methylation - Adding of a methyl group to cytosine swtiches off genes by preventing RNA polymerase from attaching
Histone Acetylation - RNA polymerase can’t bind to RNA bound tightly round histone proteins
- Adding acetyl group to lysine amino acid changes structure of histone protein loosening the DNA around it
Micro RNA - Binds to messenger RNA and thus prevents ribosomes from binding and creating proteins

Question 3

What is epigenetics?

Answer 3

Epigenetics is the study, in the field of genetics, of cellular and physiological phenotypic trait variations that are caused by external or environmental factors that switch genes on and off and affect how cells read genes instead of being caused by changes in DNA sequence
Hence epigenetic research seeks to describe dynamic alterations in the transcriptional potential of a cell. These alterations may or may not be heritable

Question 4

What role does epigenetics play in natural selection?

Answer 4

If heritable variation translates into phenotypic variation and ultimately fitness differences between individuals then epigenetic processes may provide a second system of heritable variation for natural selection to act upon - similar to the one based upon genetic variation
Epigenetic variation, unlike genetic variation, may be altered directly by ecological interactions and may therefore provide an additional, accelerated pathway for evolutionary change

Question 5

Examples of plant plasticity

Answer 5

Acacia drepanolobium - responds to herbivores by increasing spike length and number
Ranunculus aquaticus - responds to water level by altering leave structure

Question 6

Examples of plasticity in response to density

Answer 6

Hardie, 1981 - Aphis fabae (wing/non-wing)
Wilson et al., 2002 - Schistocera gregaria (melanism)
Reeson et al., 1998 - Spodoptera exempta (melanism)
Cotter et al., 2004 - Phenoloxidase resistance to pathogens

Question 7

Examples of diet plasticity

Answer 7

Apis melifera (honey bee, caste determinant)
Onthagophagus nigriventus (dung beetle, dung ball)
Nemoria arizonaria (Pine tree)

Question 8

Examples of abiotic plasticity

Answer 8

Marchinko, 2003 - Barnacles response to water current

Simpson, 2011 - Bycyclus anynana (Squinting bush brown, response to temperature)

Question 9

Examples of predation plasticity

Answer 9

Miner et al., 2005 - tadpoles

Schmitz et al., 2003 - spiders

Question 10

Examples of parasitism plasticity

Answer 10

Chadwick & Little, 2005
- Daphnia magna parasitised by microsporidium respond by producing more offspring in the early stages of exposure to compensate for the inability to do so later on

Singer et al., 2009
- Wooly bear caterpillar (Grammia incorrupta) responds to parasitism by the tachinid fly by self medicating, feeding on potentially toxic leaves that the non-infected caterpillar would avoid.