Lecture 22- Form and Function I Flashcards
What is natural selection?
The process by which individuals with certain heritable traits tend to produce more offspring than individuals without those traits
Where does natural selection occur
In populations, and often leads to phenotypic differences between populations
What is an adaptation?
A heritable trait that increases the number of offspring in an organism by increasing survival and increasing reproductive output. Adaptations can be produced by natural selection
Galapagos finch example
In the Galapagos Islands (500 miles off of the coast of Ecuador), there are around 15 different finch species that evolved from a single species that arrived from South American 2 mya
Why do different species of Galapagos FInch have different beak forms?
Beak forms are correlated with diet, the size of beak determines which seeds a finch can eat. Very thin beaks cannot crack big seeds
The evolution of beak size
Studied for 40 years of the species Geospiza Fortis by Peter and Rosemary Groat on Daphne Major, the beaks of the birds are measured each year. IN the year 1977 there was a drought causing only the big and tough seeds to be available. The next year’s birds (1978) were found to have an average beak depth 1/2 mm greater.
Why do different species of Galapagos finches have different beak forms?
Beak form has evolved by natural selection, beak forms are an adaptation to special diets, beak form matches beak function
Mantis Shrimp example
Mantis shrimp have club-like appendages of speed of 23 m/s thru water. They produce extreme forces, as strong as a .22 bullet and can break through endoskeletons of prey.
What is acclimatization?
Phenotypic change in response to change in the external environment. A trait that is due to acclimatization is not a heritable trait. However, acclimatization itself IS heritable
Examples of acclimatization
Increase in hemoglobin in mountain climbers, increase in melanin production in humans exposed to intense sunlight
Why are traits not always optimal? (trade-offs)
Trade offs are inescapable compromises between traits, structures, and physiological processes.
Examples of trade-offs: crickets
Male crickets produce a spermatophore that includes a sperm packet and a gelatinous mass. The more that the female cricket eats of it, the more eggs are fertilized. However, male crickets do not produce too many spermatophores as it causes their immune function to decrease.
Examples of trade offs: T-rex
T. Rex has small forelimbs, which can be beneficial to help titillate females during sex, to hold prey, and to get up off of the ground. As the head gets bigger, the limbs get smaller during development.
