Author’s Note

hello there friend! welcome to the LAST cram sheet of AP bio on unit 8: ecology !! I wish you the best on your studying adventures and the EXAMMMM

• like this cram sheet? I made more ! check it out at my profile ;))

• external links to other resources will also be linked to help you better understand this topic !!!!

╭ Other Resources :

:: cararra ﹒﹒ 42 min ap bio review video based from the campbell biology 11th edition textbook!

:: khan academy ﹒﹒the entire unit 7 course from khan academy!!

:: fiveable ﹒﹒ reviews unit 7 with articles and quizzes for you to practice your knowledge on!

﹙✦﹚﹒﹒please note that abbreviations will be used throughout this guide (kept at a minimum!)

﹙8.1 - Responses to the Environment﹚

✦﹒an organism’s behavior and physiological response is related to environmental changes

• stimulus is a combination of signals, or internal/external signal that causes response

• behavioral response affects the overall fitness

  • communication between organisms can change behavior (signaling behavior)

  • signaling behavior can result in differential reproductive success

• communication mechanisms can be visual, audible, tactile, electrical, and chemical signals

  • helps indicate dominance, find food, establish territory, and ensure reproductive sucess

✦﹒behaviors can be . . .

• innate, where they are genetically controlled and can occur w/o prior experience/training

• learned, developed as a result of experiences

  • natural selection favors these, increasing reproductive success and survival

• cooperative, involving teamwork between same species, increasing individual fitness survival

﹙8.2 - Energy Flow Through Ecosystems﹚

✦﹒there are different strategies that help regulate temperature and metabolism

• endotherms use thermal energy from metabolism to maintain body temperature

  • can be from heart rate changes, shivering, fat storage

• exotherms lack these, relying on behaviors

  • ex: moving to sun/shade

✦﹒energy is used to grow + reproduce

• metabolic rate is the amount of energy used by animal over a specific time

  • gain → energy storage/growth

  • loss → loss of mass/death

  • smaller organism → higher rate

• many offspring → less energy efficient, common in unstable environments

• few offspring → more energy efficient, common in stable environments

• changes in energy causes . . .

  • changes in population site

  • ecosystem disruption by changes in resources and trophic levels

✦﹒organisms have different roles in their ecosystem

• trophic levels are the position the organism has on the food chain

  • transfer of energy is inefficient (organisms get 10% of energy from their prey)

  • limits food length and population size

• autotrophs capture energy from physical or chemical sources from the environment

  • are photosynthetic/chemosynthetic

• heterotrophs capture energy present in carbon compounds frm organisms

﹙✦﹚﹒trophic levels, autotrophs and hetrotrophs, and endotherms and exotherms are perhaps the most important thing to note in this section

﹙8.3-8.4 - Population Models﹚

✦﹒population growth depends on many factors—

• reproductive maturity age

• # of offspring produced

• reproduction frequency

• survivorship of offspring → reproductive maturity

  

✦﹒reproduction w/o constraints causes exponential growth

• exponential growth is a sharp increase of growth

  • happens in ideal conditions

  formula for exponential growth. exponential growth is represented graphically on the right.

• r_max = (B-D)/N

✦﹒population density refers to how close individuals within a population live near one another

• lots of food → higher density

  • high reproductive rate, limited space

• limited food → density may decrease

  • low reproductive rate, individuals can spread out in limited space

✦﹒limitations occur because of these factors—

• density dependent are abiotic/biotic factors whose affect depends on a population’s density

  • ex: competition, territoriality, disease, predation

• density independent affects population regardless of a population’s density

  • ex: natural disasters, and pollution

✦﹒logistic growth model describes growth that starts as exponential, but then stabilizes at a certain point

formula for logistic growth. to the right is what logistic growth looks like graphically.

• carrying capacity is the maximum amount the environment can substain

  • caused from density factors

  • upon exceeding the capacity, limiting factors bring it down, and fluctuations may occur

  !! tips for calculating things using logistic growth model

  • when asked to find the expected population size

    • plug all values into the equation. it should give you dN/dt, which is the value of how much more individuals would be added

    • add that value with N (population size)

  • when asked to find the r_max

    1. subtract population after one year by starting population to find dN/dt

    2. combine already given terms

    3. divide that value to the other side

    

  • when asked to find the carrying capacity

    1. subtract population after one year by starting population to find dN/dt

    2. multiply K on both sides

    3. find the value of r_max*N and distribute that value into (K - N)

    4. move the distributed K to the other side

    5. divide the coefficient of K on both sides

    

╭ Other Resources :

:: bozeman science ﹒﹒ 11 minute video explaining in depth about logistic growth and its meaning!!

:: lasseter’s lab ﹒﹒ introduces populations growth equations and problems practice math problems! its 6 minutes long.

﹙✦﹚﹒math = important. this is perhaps the HARDEST math in AP bio so it is HIGH ENCOURAGED to practice!

﹙8.5-8.6 - Community & Diversity﹚

✦﹒communities are described based on species composition + diversity

• species diversity is the variety of species and quantity of individuals included in each species

  • ex: a shark and turtle species w/15 sharks and 62 turtles

• species compositions is the identity of each species

  • ex: ocean community has 2 species of angel fish— namacanthus paru and pomacanthus xanthmetopan

✦﹒the Simpson’s Diversity Index measures biodiversity using random samples from the environment

• higher index value → more diverse

✦﹒interactions among populations determine how they access energy and matter

• positive interactions —

  • mutualism is where both species benefit (+/+)

  • commensalism is where one benefits, but the other is not harmed or helped (+/0)

• negative interactions —

  • predator-prey is where one uses the other as a food source

  • parasitism - one benefits, other is harmed (+/-)

  • there is also neutral interactions → none is benefited or harmed (0/0)

• interactions can be modeled

  • ex: predator-prey

    

  • inc in prey → inc in predator

  • inc in predator → dec in prey

• trophic cascade is the negative effect the removal/decrease of a key species has on tropic levels

  • causes exponential growth/death

  • interrupts flow of energy

  • key/keystone species are species that community structure depends on

    • smaller population, removal of this = ecosystem downfall

    • overpopulation → depletion of resources

• niche partitioning is the decrease in competition over limited resources because of each species accessing resources differently

✦﹒abiotic and biotic factors help maintain biodiversity

• abiotic factors are the non-living things that help maintain diversity in the environment

  • ex: includes climate, water + nutrient availability, light availability

• biotic factors are the living things that help maintain diversity in the environment

  • includes producers, as many depend on them for food + habitats

    • reduces erosion; areas that have NO life

  • includes dominant predators, which help stabilize prey population

╭ Other Resources :

:: amoeba sisters ﹒﹒ a 6 minute video covering symbiotic relationships! (mutualism, parasitism, etc.)

:: bozeman science ﹒﹒ 7 minute video covering biodiversity and well as the importance of a keystone species

﹙✦﹚﹒know each of the individual interactions (ex: mutualism), the difference between abiotic and biotic factors, trophic cascades, keystone species, and niche partitioning!!!!

﹙8.7 - Disruptions to Ecosystems﹚

✦﹒invasive species are non native to the environment, and harms the community it is introduced to

• exploits new niches

• outcompetes other organisms for resources

✦﹒human activity can disrupt/change the ecosystem

• this includes deforestation, urbanization, erosion, pollution, extinction, and climate change

• overpopulation of humans can easily spread diseases which devastates native species

✦﹒geographical and meteorological events can cause. . .

• large habitat disruption

• chemical disruptions

• extinction

• biogeographical studies illustrate these changes

  • analyzes species distribution

  • can characterize biome

﹙✦﹚﹒don’t really worry about this part, its pretty logical and straightforward