Evolutionary Development Flashcards
(24 cards)
evolutionary constraints
a specific trait won’t evolve a certain way - for example, due to a correlation with another trait, or lack of existing variation
butterfly eyespots
size of butterfly eyespots can evolve independently in artificial selection experiments, but the color combinations cannot evolve to be different
gives us info on the processes that forge traits
ontogeny
development of an organism from embryo to adult
diverse species share…
embryonic features such as limb bud paddles, pharyngeal arches, tails, etc.
allometry
unequal scaling; different parts change size at different rates
ex. bats’ fingers grow way longer than ours, comparatively; tomatoes have small sepals and ground cherries have big ones; elephant tusks are just teeth that have grown bigger for longer
heterochrony
unequal change in timing of development, such as neoteny i.e. some body parts mature faster than others
neoteny
adult form maintains its juvenile appearance but is sexually mature
ex. axolotls - never metamorphosize from larva salamander form to adult salamander form
heterotopy
change in the location of where a developmental cascade takes place
ex. monstera vine growing aerial roots along its stem
individualization
serially homologous structures diverging in development and function
ex. synapsids (mammalian precursors) had uniformly sharp teeth; mammals then evolved teeth of all different shapes for different functions
process-based metrics of diversity can arise through
variation in regulatory mechanisms
transcription factors/trans regulatory elements
control whether a gene is transcribed - form a complex to interact with enhancers
TFs are coded for by DNA distant from the gene they regulate
enhancers/cis regulatory elements
interact with TFs
control the transcription of the same DNA they are part of
transcription can differ
based on what TFs bind to which enhancers, and when
methylation/epigenetics
turns transcription off when certain cytosines followed by guanosine residues are methylated -> methylation may be maintained in newly synthesized sections of DNA
alternative splicing
various exons of a eukaryotic gene are often differentially spliced into many
isoforms that have different functions, and may be expressed in different cells
isoforms
alternatively spliced transcripts within genes - may be very common
homeotic mutations
can transform one body part into another
morphogen gradients
establish domains of the embryo, and direct the fates of each domain
changes in morphogen gradients…
alter the resulting body plan
ex. fly growing another wing domain where its leg domain should be
homeobox genes are:
shared between almost all species (except sponges), and reused in homologous structures within a body
ex. if you are a bug with lots of legs you will use the same hox genes for all your legs
genetic toolkit
some hox genes that encode transcription factors are like tools that can be used in different ways in a wide variety of situations - TFs can bind to a lot of different enhancers
evolvability
not all phenotypes are possible due to size limitations and physiological limitations
pleiotropy constraints
alleles that are incompatible with each other -> individuals with both will not survive
phenotypic plasticity / GxE interactions
in different environments, the same genotype can generate different body plans
(different from how in different environments the same phenotype is optimal, or different phenotypes of different genotypes are optimal but they do not fall on the same genotype)
