Chapter 3

Adaptation to environmental factors

• Change factors that limit growth (amount of food, composition of air)
• Change Tolerance Range (Temperature tolerance, ph tolerance )
• Change Behavior to adapt beyond Range ( avoid cold areas )

Limiting environmental factors

• physical factors (strength, ability to fly)
• Physical resources
• Tolerance bounds

optimality and Principle of allocation

Adaptation to one challenge may decrease for another. The more an organism adapts to a stable environment (optimality), the less able it is to adapt to new environments that pose new challenges (moving from hot to cold, fresh water to salt water or vice versa)

• Large beaks make it easier to break large nuts, but harder to eat insects out of trees.
• Homeostasis allows humans to survive in a variety of environmental conditions, but requires more (is limited by) food.

Normal Distribution and measures of variation

Many biological factors rely on modifications to the normal distribution.

• quantified as a probability or confidence interval (95% of samples fall within this range of values)
• \(\text{Sample Variance} = \frac{\sum_1^n (\bar x - x_i)^2}{n-1} = s^2\)
• \(\text{Sample Mean} = \frac{\sum_1^n}{n} = \bar x\)
• \(\text{confidence statistic (percentage)} = 1-\alpha\)
• \(\text{confidence interval} = \bar x \pm t_{1-\alpha} * s/\sqrt n\)
• \(\text{Standard Error (Estimate of the mean)} = \frac{s^2}{n}\)

Description of the plots used in ecology

• y axis refers to the frequency of individuals (higher is more)
• x axis refers to some limiting factor (food, temperature)
• Peak refers to the mean of the sample

P Value

The P value is the probability that the Null hypothesis is true. This value is calculated with a statistical test (t test when using a sample).

Example

• \(H_0 = \text{Cancer is randomly occuring}\)
• \(H_a = \text{Cancer is caused by radiation damage}\)
• \(P < 0.05\)
• There is less than a 5 percent chance that cancer is randomly occurring.

behavioral Thermoregulation.

Animals will move to areas that are conducive to their optimal temperature range.

• Snakes bask in the sun to warm up (ectotherms)
• Humans will go inside (or put on clothes) to warm up (endotherms)
• Monkeys will bathe in hot springs in cold climates. (endotherms)

Adaptive radiation

The tendency for species to diversify to fill open ecological niches.

• Early Plants
• Finches

Osmoregulation (water stress) and photosynthesis

Organisms alter their internal concentration of solute (or consume water) to regulate their internal water content.

• Skin and scales prevent unintended evaporation of water
• C3 pathway is shared by all plants (the calvin cycle)
• C4 pathway allows plants to save water by closing the stomata when necessary.

Adaptation vs Plasticity

Some animals have larger optimal ranges of physical resources than others (plasticity)

• Evolution thorugh natural selection adapts organisms to their environments
• Plasticity refers to the ability of an organism to survive in different environments
• Humans could be said to have high plasticity due to our tool making
• Octopi make estensive use of RNA editing sites to alter their expression Octopus RNA editing sites (plasticity?)