AP BIO - Unit 8 FRQ

Animal Communication Strategies

Visual communication: body language, exaggerated displays - day, fast
Auditory communication: calls and sounds - day/night, fast
Chemical communication: pheromones are passed between animals - day/night, slow
Tactile communication: touch conveys information - day/night, fast
(VACT)

Exponential vs Logistic Growth Patterns

An exponential growth pattern starts with a lag phase, then the population grows quickly and exponentially. However, this growth is not unlimited, as it will eventually crash when the population ends up depleting its resources. This pattern is common in R-strategists, adapted for unpredictable environments, and associated with density independent factors and semelparous reproduction. Examples include insects and invertebrates.
A logistic growth pattern also lags and then grows exponentially, but once it reaches the carrying capacity (K), it begins to fluctuate around that line. This puts it into a relatively stable equilibrium phase. This pattern often occurs in K-strategists because it works better in unchanging environments. Usually it is associated with iteroparous reproduction. Examples include larger mammals.
Both patterns display a lag phase at first, then rise exponentially, but logistic growth hits carrying capacity while exponential growth will eventually crash due to outside factors. They represent the two extremes of the natural world - most populations will fall somewhere in between.
dY/dt = rate. dN/dt = B - D = population growth. Rmax = maximum per capita growth rate of a population.

Reproductive Strategies and Fitness

Semelparous reproduction involves only reproducing one time during an organism's lifetime, usually producing many young at once. This is common in insects and invertebrates. This behavior is adapted to unpredictable environments and associated with R-selected populations.
Iteroparous reproduction involves reproducing multiple times throughout an organism's lifetime, along with caring for the young as they mature. This is common in birds and mammals. This behavior is adapted to stabler environments and associated with K-selected populations.

R-selected vs K-selected populations

R-selected populations are opportunistic and maximize their reproductive rates. They are adapted for fluctuating environments. They have a J-shaped growth curve and are often small with a short lifespan. They usually do not care for their offspring.
K-selected populations are competitors and hover near carrying capacity. They are adapted for predictable environments. They have an S-shaped growth curve and tend to be specialists, with a large size and a long lifespan. They tend to care for their offspring.

Environmental influences on behavior

While some behaviors are innate, others are learned from the environment surrounding that organism and the conditions affecting it.
Some examples include habituation, social interaction (which helps learning), observation and imitation, and associative learning.
Classical conditioning: an involuntary response becomes associated with a certain stimulus. Think of Pavlov's dogs.
Operant conditioning: rewards or punishments strengthen the link between a certain stimulus and a specific responding behavior. Think of Skinner's rats.

Age-structure diagrams and demographic transitions

In a pre-reproductive population, most individuals are in pre- or current reproductive stages. The population is growing.
In a reproductive population, all three groups are relatively similar sizes. The population is stable.
In a post-reproductive population, most individuals have aged past reproductive ages. The population is decreasing.
Demographic transition occurs when a population moves from high birth and death rates to decreasing the death rate, and then decreasing the birth rate.
Most MDCs have a stable population, while LDCs have a growing (prereproductive) population. This reduces living conditions because the population is too large for available resources to support it sufficiently. To help transition LDCs to a more stable environment, the growth rate must be reduced. This can be achieved through a number of tactics, such as better education for women, family planning, and delaying childbearing.

Density-independent and density-dependent regulators of population size

Density-independent factors have the same impact on all populations, regardless of their size. Some examples include natural disasters like tornadoes and floods. They are typically abiotic.
Density-dependent factors affect larger populations more heavily than smaller populations. Some examples include competition, predation, and disease. They are typically biotic.

Altruism vs self-interest

Altruism, defined as self-sacrifice for the gain of another, does not truly exist (at least the animal kingdom). Everything is done for some sort of a reward, even if it may not appear so. For the purpose of their own fitness and continuing their genetic line, animals do everything out of self-interest.
Direct selection is between a parent and their offspring. Kin selection is between a relative and its indirect descendant.
Reciprocal altruism is a sort of trade, or bargain. Both organisms benefit, but the debt is repaid at a later time. "I'll scratch your back if you scratch mine."

Measuring biodiversity

Simpson's diversity index is used to measure biodiversity. It represents the probability that two individuals randomly selected from a sample will belong to different species.

Innate behavior

Research suggests that some behavior has a genetic basis. That is, the genes in one's body can code for a certain behavior without needing it to be learned.
For example, a hybrid between two lovebirds carried intermediate lengths of nesting material and was often caught between where to carry it: in its beak or in its rump feathers.
Twins raised separately from each other ended up sharing many of the same characteristics and preferences.

Ecological pyramids

An ecological pyramid models the energy that is passed between each trophic level of a food chain. Typically, only 10% of the energy gets passed on to the next level, because the rest is lost to the organism performing its everyday and physiological functions - this keeps food chains relatively short.
An ecological pyramid might be built with numbers, biomass, and/or energy.

Growth rate and biotic potential

Growth rate (per capita rate of increase) = birth rate - death rate
Biotic potential is the maximum reproductive rate, aka the highest possible growth rate. It depends on conditions such as the age of first reproduction, the average number of offspring, how often each individual reproduces, and chance of survival until age of reproduction.

Density and distribution patterns of organisms

Density is the number of individuals per unit area.
The most common distribution pattern is clumped, in which organisms cluster around resources. The environment is varied.
In a uniform distribution pattern, organisms are spread across the habitat evenly. The environment is uniform, and competition is high because space is tightly regulated.
In a random distribution pattern, organisms are scattered across the habitat without any organization. The environment is still uniform, but competition is low.

Strategies organisms use to acquire and use energy to maintain homeostasis

Poikilotherms/ectotherms, also known as cold-blooded, rely on their outside temperature to regulate their own internal temperature. This saves energy, but also limits the range of habitats in which they can live.
Homeotherms/endotherms, or warm-blooded, can regulate their own body temperature using physiological processes. This costs more energy, but allows them to inhabit a wider range of habitats and adapt more easily.
Other responses include anhydrobiosis (dehydration), hibernation (an extended sleep), migration (seeking resources), countercurrent exchange (fluids run in opposite directions), and mutations (genetic changes).

How climate affects ecosystems

Climate is dependent on temperature, rainfall and topography as well as the relationship the air has to bodies of water. All of these items can influence where species live and what adaptations they need.
Climate determines the everyday weather conditions of a biome. It is used as one of the identifying mechanisms to organize biomes.

Predator/prey interactions

Predators hunt prey, sometimes so much that they reduce the prey densities and lower their own population.
Relationships often fluctuate over time, rising and falling together. One example is the lynx and snowshoe hare cycle.
Coevolution occurs when both the species pressure each other to evolve. They both try to out-adapt each other.

Nutrient cycles vs energy flow

The first and second laws of thermodynamics state that energy cannot be created or destroyed, only transformed. That energy flows through a food web, changing forms as it is passed between organisms and losing heat at every transformation. The energy also flows between organisms as they feed on each other, because it is passed between trophic levels.
Nutrients start in producers, which are then consumed by primary consumers, then secondary consumers, etc. Once these heterotrophs die, they will be digested by decomposers, and the nutrients return to the earth, where they will start their cycle again in another producer.

Direct values of biodiversity

Medicinal value means that preserving biodiversity could lead to us finding new drugs and treatments, especially in the endangered rainforests.
Agricultural value means that wilder and hardier crop strains could provide disease-resistant and pest-resistant genes to cultivated, genetically-similar strains.
Consumptive value means that cultivating crops and domesticating animals could result in more resources for us.

(MAC)

Food web

A food web is a representation of a certain ecosystem and the relationships that the organisms within that ecosystem share. It shows all the possible feeding relationships at each trophic level in a community and maps out the paths of energy flow.
It is more realistic than a food chain because most organisms depend on more than one food source.
Some examples include grazing food webs (starts with grass) and detrital food webs (starts with detritus).

Behaviors that increase fitness

Organisms must learn to adapt to their environment, thereby increasing their own odds of survival and their individual fitness. To increase fitness, organisms will migrate, defend their territory, pick mates depending on their desirable traits, and more.

Competitive Exclusion Principle

No two species can occupy the same niche indefinitely at the same time.
One possible outcome is that one species replaces the other, which dies out.
Another possible outcome is resource partitioning. Both the species shift niches so the area of competition is narrowed. This can lead to character displacement, which can lead to speciation.

Techniques in habitat preservation and restoration

To preserve a habitat, humans might protect keystone or flagship species. We can stop source populations from migrating into sink habitats and prevent fragmentation of habitats.
To restore a habitat, restoration should begin immediately, techniques should mimic natural processes, and restoration should focus on sustainable development.

Biogeochemical cycles

In the water cycle, water is found underground, in the atmosphere, and as surface water, both in liquid and solid form. It evaporates, condenses in the air, falls as precipitation, and returns to the ground. Humans often pollute water and cause sinkholes by draining naturally-occurring aquifers.
In the carbon cycle, CO2 in the atmosphere is taken in by plants during photosynthesis, which are eaten by consumers and released back into the atmosphere through cellular respiration. More CO2 is being released into the environment than removed due to burning of fossil fuels, the destruction of forests, and the greenhouse effect: this creates a positive feedback loop.
In the phosphorus cycle, the reservoir for phosphorus is located within rocks - weathering can release it into water, from which it is usually immediately removed by autotrophs. Humans might dump large amounts of phosphorus into ecosystems, oversaturating them with nutrients. This might cause things like eutrophication.
In the nitrogen cycle, nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia, then nitrifying bacteria convert it into nitrite, then nitrate. Plants can use the nitrate, then animals eat the plants, and decomposers return it to the soil. Denitrifying bacteria return it to the atmosphere. Humans produce nitrous oxides and fossil fuels, contributing to acid rain and photochemical smog.

Three components of biodiversity

Genetic diversity is the variety of genes or inheritable characteristics that present in a population.
Community diversity is the variation of species composition in a community. (The Simpson's diversity index equation can be used for this.)
Landscape diversity is the variety of ecosystems in the biosphere.

(GLC)

Symbiotic relationships

They occur between two different species. At least one species benefits.
In parasitism, one organism benefits at the expense of another. An example is a tick living on a dog.
In commensalism, one organism benefits and the other neither benefits nor suffers. An example is a bromeliad growing higher up on a tree.
In mutualism, both organisms benefit. An example is birds picking gunk/food out of an alligator's teeth.

Indirect values of biodiversity

Biodiversity contributes to biogeochemical cycles at a lower cost than man made processes would.
Decomposers can dispose of waste efficiently.
Forests act as "sponges" for freshwater.
Intact ecosystems naturally retain soil and prevent erosion.
Trees provide both shade and natural air conditioning. Tropical rainforests serve as sinks for carbon dioxide.
Ecotourists might spend money to enjoy natural habitats, and that money can be used to support conservation efforts.

Ecological succession

After a disturbance, an environment recovers in stages. Ecological succession involves a series of species replacements as an environment rebounds from a disturbance.
Primary succession begins without soil, possibly after a fire. Pioneer species must break up the rock and create soil, so other plants can begin growing.
Secondary succession begins with soil.

Five main causes of extinction

Habitat loss removes the places in which organisms can live. Diversity hotspots are especially vulnerable to this because they are rather small and have little area, but lose more species for every bit of habitat they lose.
Alien species might invade otherwise-balanced habitats and throw off a dynamic equilibrium. Humans can break natural barriers that keep alien species in and cause the disruption of a food web.
Pollution, caused by humans disrupting natural habitat through situations like the greenhouse effect and ozone depletion, is changing environments faster than organisms can adapt.
Overexploitation occurs when humans remove so many animals of a population from their natural habitat that that population is unable to recover. This is often driven by a positive feedback loop of rarity and desire.
Disease can spread to species through domestic animals when humans encroach on natural territory.
(HEPOD)