2. • Evolutionary developmental biology
• Compares the development of different organisms to try
to understand ancestral relationships between them and
the developmental mechanisms that cause evolutionary
change
• Involves the discovery of genes that control development
3. • Genetic changes, also called genetic innovations,
cause structural changes in organisms
• Advantageous innovations can result in species development
• Proteins control developmental changes
• Promote morphological changes during evolution
4. • Genes that play a role in development may influence cell
division, cell migration, cell differentiation, and cell death
• Interaction among these 4 processes produces an
organism with a specific body pattern, or a pattern
formation
• Developmental genes play a key role in the evolution of
certain traits and affect and organisms phenotype
• Variation in their expression can result in new traits that
promote speciation
5. • Chicken foot & Duck foot
Comparison
• Due to differences in
expression of 2 cell-signaling
proteins
• BMP4: causes cells to
undergo apoptosis and
die
• Gremlin: inhibits the
function of BMP4 and
allows cell to survive
6. • Mutations on the expression of BMP4 and gremlin
provided variation
• Terrestrial settings: nonwebbed feet are an advantage
• Enable individual to hold onto perches, run easily, catch prey
• Natural selection favors nonwebbed feet
• Aquatic environments: webbed feet are an advantage
• Act as paddles for swimming
• Natural selection favors webbed feet
7. • Found in all animals
• Variation in the Hox genes may have spawned
the formation of many new body plans
• Number and arrangement of Hox genes varies
among different types of animals
• Increases in the number of Hox genes may have
led to greater complexity in body structure
8. • Encode transcription factors that act as ‘master control’
proteins which direct the formation of certain body regions
• Each Hox gene controls a group of regulatory genes,
which in turn regulate the expression genes that ultimately
affect an organism’s morphology
• Different Hox genes are expressed at different regions
along anteroposterior axis
9.
10. • Three lines of evidence support the idea that Hox gene
complexity has contributed to the evolution and
speciation of animals with different body patterns:
1. Hox genes control the fate of regions along the
anteroposterior axis
2. Organisms with more Hox genes and Hox clusters tend
to have greater body complexity
3. Hox gene evolution and animal evolution bear striking
parallels
11. • Genetic variation can influence morphology by controlling the
relative growth rates of different parts of the body during
development
• Heterochrony: evolutionary changes in the rate or timing of
developmental events
• Compare growth of head between human and chimpanzee
• Paedomorphosis: sexually mature organism retains traits
typical of the juvenile stage of the organism’s ancestor
12.
13. • Explaining how a complex organ comes into existence is a
major challenge
• Researchers have discovered many different types of eyes
• Thought that eyes may have independently arisen many
different times during evolution
• Pax6 is a master control gene that controls the expression of
many other genes and influences eye development
• Present in rodents and humans
• Eyeless gene is found in Drosophila, fruit flies, and induces
eye development
14.
15. • Eyes of Drosophila and mammals are evolutionarily derived
from a modification of an eye that arose once during
evolution
• If Drosophila and mammalian eyes had arisen
independently, the Pax6 gene from mice would not be
expected to induce the formation of eyes in Drosophila
• Recall: Darwin hypothesized that the eyes from many
different species all evolved from a common ancestral form
consisting of one photoreceptor cell and one pigment cell
• Over time, simple eyes evolved into complex eyes by
modifications that resulted in additional cell types
• Lens cells, muscle cells
• Others argue that Pax6 only controls eye development up to
a certain extent and that different types of eyes evolved
independently
