Timing

What is the main theme of this lecture?

How the timing of developmental events affects organismal form, function, survival, and evolution.

Why is timing important in development?

Because changes in when developmental events occur can alter phenotype, performance, and evolutionary outcomes.

Who emphasised that evolution of form occurs through development?

Wallace (2002).

What are the three main learning outcomes of this lecture?

1. How developmental timing is measured

2. Why timing matters biologically

3. How timing may change in the Anthropocene

What are developmental stages?

Distinct phases in development (e.g. cleavage, gastrulation, organogenesis).

What are developmental sequences?

The order in which developmental events occur.

What are developmental timings?

When specific developmental events occur relative to time or other events.

What is heterochrony?

Variation in the timing or rate of developmental events within or between species.

What is EmbryoPhenomics?

A high-resolution approach to visualising temporal, spatial, and functional diversity in developing embryos.

What does EmbryoPhenomics measure?

• Timing of events

• Spatial development

• Functional changes over time

What technical factors are important when recording development?

• Resolution

• Frame rate

• Recording frequency

• Recording duration

• Magnification

Why is high temporal resolution important?

It allows precise measurement of when developmental events occur.

What is a parent–offspring breeding study?

A study comparing developmental timing between parents and their offspring.

What did parent–offspring studies show?

Developmental event timing can be heritable.

Why is heritable timing important?

It allows developmental timing to evolve via natural selection.

What organism is used as a key case study?

The marine gastropod Littorina obtusata.

What aspect of development was studied in Littorina obtusata?

Cardiac and cardio-respiratory development.

What happens if cardiac development is mistimed?

Embryos may fail to survive, especially under low oxygen conditions.

Why is hypoxia important in this study?

Survival depends on timely development of cardio-respiratory systems in low oxygen environments.

What key conclusion came from this study?

Differences in developmental timing can determine life or death.

What is phenomics?

The acquisition of high-dimensional phenotypic data across the whole organism.

How is phenomics different from genomics?

Phenotypes are far more complex and multidimensional than genomes.

What challenge does phenomics address?

Linking genotype to complex, multivariate phenotypes.

What does “putting Humpty Dumpty back together” mean in phenomics?

Integrating multiple traits to understand the whole organism.

What is the Human Physiome Project?

An effort to model and integrate human physiological systems.

How is phenomics relevant to medicine?

It supports personalised and individualised medicine.

Where is plant phenomics used?

At centres like the National Plant Phenomics Centre (Aberystwyth).

What is the Anthropocene?

A geological age where human activity dominates environmental change.

Why is developmental timing important in the Anthropocene?

Environmental changes may alter developmental rates and survival outcomes.

How might climate change affect development?

By shifting developmental timing, leading to mismatches with the environment.

How does evolution act on development?

By modifying the timing, rate, and sequence of developmental events.

Why is timing considered a powerful evolutionary mechanism?

Small timing shifts can cause large phenotypic changes.

What links development, evolution, and survival?

Developmental timing.

What is the main takeaway from this lecture?

Timing is a critical, heritable, and evolutionarily important component of biological development.