Selective Pressures The making of a species

Selective Pressure Natural Selection occurs over successive generations Evolution works on a species level by describing how the species attains the genetic adaptations that allow them to survive in a changing environment.

Special Note Without a changing environment, neither evolution nor natural selection would occur.

Genotype Fitness Are the genes present in a population best suited to allow the population to continue to reproduce?

Types of Pressure Physiological Stress Predation Competition Luck

Geologic Isolation Geologic isolation creates a unique situation that often forces evolution to occur through speciation The Galapagos Islands offer the best example of this phenomenon Ring Species A modern example of speciation through geologic isolation.

Case Study Good Trait? Bad Trait? Congenital condition known as myotonia congenitamyotonia congenita Causes the goat's muscles to tense up when the animal is startled and don't immediately relax. muscles The gene called CLCN1 (Chloride Channel 1).

Under normal conditions The animal's eyes and ears relay the perceived threat to the brain, which then sends an electrical signal to the skeletal muscles, causing a momentary tensing.eyesearsbrain electricalmuscles This is often referred to as the fight or flight response.

Fight or Flight Just think how it feels to be startled. You'll find your voluntary muscles contract and tighten for a second. This is your brain telling your muscles that the time has come to possibly confront or run away from an immediate threat. Normally, this tensing is followed by an immediate relaxing of the affected muscles, allowing you to turn and run away from a perceived threat.

The Biology of the Condition Positively charged sodium ions relay the brain's message for the muscle cells to contract. Negatively charged chloride ions, which CLCN1 affects, tell the muscle cells to relax. Mytonia congenita results in an abnormal channel of chloride ions, which throws this relationship out of balance.

The Question? What is the Genotype Fitness of the fainting goat in the wild? Types of selective pressure? – Physiological Stress – Predation – Competition – Luck

Would these goats survive in the wild? Artificial Selection In fact, they would not survive in the wild. Bred as pets Used by goat herders as bait animals for predators.