| A | B |
|---|
| isometric growth | Newborns have the same proportions as adults |
| allometric growth | Organism has body part(s) that change less than the rest of the body. Most common form of growth. Ex. In humans, head size changes less than rest of the body |
| Variation can be explained by: | Allometry (shifts in relative growth rates), Heterochrony (shifts in timing of developmental stages), and Serial Homology (segmentation that allow for variation across the body) |
| Heterochrony | Evolutionary change in the rate or timing of developmental events. Ex. Salamanders usually have an egg to larval to adult life cycle, but some exhibit paedomorphosis, which means that an organism is mature but exhibits larval morphology |
| Serial homology | Homologous structures occur in "series" down the animal's body, allowing for some to be modified without reducing original function of limbs. |
| Hox genes | In animals, these genes determine a segment's identity, leading to appropriate apendage development. In fruit flies, manipulation of the bithorax group results in flies with two thorax, and manipulation of the antennapedia group results in flies that have legs where antenas should be |
| MADS-box genes | These are homeotic genes in plants that impact development of different whorls in flowers |
| Changes in Hox gene expression can result in what? | Variation in body plan. Ex: the origin of jaws was the result of gene duplication events that produced more hox genes in a hypothetical early vertebrate, resulting in 4 hox clusters. This freed up the ability for a structure (gill arches) to evolve into a jaw |
| Behavior is defined as | An action carried out by muscles or glands under control of the nervous system as the result of a stimulus. Ex. when a chameleon changes color to adapt to its surroundings |
| A fixed action pattern | is a sequence of unlearned acts directly linked to a simple stimulus. It is essentially unchangeable, and continues once initiated Ex. Greylag goose will keep rolling egg even when egg is removed |
| sign stimulus | s simplified trigger for an action pattern, if it is too simple it can be abused and manipulated. Ex Himalayan cuckoos lay their eggs in the nests of yellow-bellied prinia, and the adults respond to the stimulus (the egg) and treat it as their own |
| proximate causation | explanation for HOW physiologically or developmentally a behavior occurs |
| ultimate causation | explanation for WHY a behavior has evolved |
