Ch. 21 Populations and Communities

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Ch. 21.1 Living Things and the Environment

Listen while Ms. Helm reads the story: p. 704

Vocabulary

• Organism- a living thing– Obtains food, water, shelter, and other things it

needs to live, grow and reproduce from its environment.

• Habitat – An environment that provides the things the organism needs to live, grow and reproduce.

Habitats have 2 parts:

Biotic (living, or once living)• Grass• Seeds• Berries• Hawks• Ferrets• Badgers• Eagles• Fur• feathers

Abiotic (not living)• 5 major categories:• 1. Water• 2. Sunlight• 3. Oxygen• 4. Temperature• 5. Soil

Levels of Organization

»FOLDABLE:• Organism (smallest – 1 living thing)• Species (many of the same organism)• Population (All the members of the same

species in an area)• Community (all the populations in an area)• Ecosystem (all the communities in an area)

Ch. 21.2 Studying Populations

Determining Population Size

• In order to study something, you need to know how big the population is, and how it changes over time.

• Some methods of determining the size of a population are direct and indirect observations, samplings, and mark-and-recapture studies.

Different Ways to Count a Population

• Direct Observation: The most obvious. You count ALL the members.

• Indirect Observation: Sometimes, the organism you are trying to study is hard to see/find. Then you have to look for SIGNS of your organism.– Counting nests of birds, holes of prairie dogs, etc.

Ms. Helm’s Favorites:

• Sampling: When it’s too hard to count each and every one:– MAKE AN ESTIMATE!– Count all the ones you can find in a small area, them

multiply to find the larger area. (exp: I have 10 acres. I count all the trees on 1 acre, then multiply by 10)

• Mark-and-Recapture:– Catch, and mark, all the ones you can find (animals).

Then come back in 2 weeks and try to catch as many as you can. See how many you caught before and compare that to the number that are new.

Mark-and-Recapture Equation

• Total Population = Number marked x total number capturedNumber recaptured (with marks)

• Try:• Pg. 719: Counting Turtles

HOMEWORK: Foldable:

• 4 methods of Determining Population Size

Fold corners in

Changes in Population Size

• Populations can change in size for a few reasons:– Births(+) and Deaths(-)– Immigration(+)/Emigration(-)– (Im = in) / (Em = exit)

Obviously…

• Growing = • BIRTHS(+) > deaths(-)• IMMIGRATION(+) > emigration(-)

• Decreasing =• Deaths(-) > BIRTHS(+)• Emigration(-) > IMMIGRATION(+)

Population Density

• Its important to know HOW MANY there are, but ALSO: how many IN AN AREA (are the spread out or crowded?)

• Sorry, here’s some math for you:• Population density = Number of individuals

Unit Area– You should be able to use this equation on the

test/quiz (no calculator).

Limiting Factor

• Remember: Factor… (biotic factor, abiotic factor… Factor = thing)

• Limiting Factor – an environmental factor that causes a population to DECREASE! (not enough food, water, space, weather, etc.)

• Its like making a cake, you might have 10 boxes of mix, but only 3 eggs. You can only make 1 cake. The EGGS are the LIMITING FACTOR! (you should be able to figure out something like this on your test!)

Space as a Limiting Factor

• Puzzle Lab?

Ch. 21.3 Interactions Among Living Things

Video Field Trip!

Hide your Critter

• Ms. Helm will give you a piece of white paper in the shape of a critter. Your job is to color it so that it will blend in PERFECTLY in a secret place in the classroom. You will tape it to the surface of something in the room. – YOU CANNOT HIDE IT UNDER/BEHIND something!– Good Luck!

Adapting to the Environment

• Natural Selection (remember!) – when the environment (mother nature) selects who lives and dies. If its cold, you need lots of fur, etc.

• Adaptations – behaviours or physical characteristics to help you survive:– Behaviour: hide when the wolf is chasing you– Physical: have thick fur in the snow

Niche

• Niche – (nitch) an N dimensional hypervolume.

• WHAT!?!?!?!?!?!?!?!!?• Basically, that special place where everything

fits in just right. Every organism has a variety of adaptations that are suited to its specific living conditions.– What makes a scorpion perfect for the desert? It

perfects fits that Niche!

Interactions

• 3 types:• Competition• Predation• Symbiosis

Competition

• Fighting for stuff, duh!– But not always physically…

• It could be racing for food (remember the bird beak lab?)

• It coold be trying to look sexy for the lady frog, etc.

Predation

• Hunting and getting eaten.• Bird eats Frog:

– Bird = predator– Eating = predation– Frog = prey

• Too much Predation = SMALLER POPULATION– Pg. 725 Math analyzing Data

Predator Adaptations

• Cheetahs run fast• Jellyfish tentacles are poisonous• Some plants have sticky bulbs to catch insects• Big eyes on owls to see at night• Sonar for bats

Prey Adaptations

• Being very alert (think sketchy deer)• Skunk spray (I’ll give you a stick eye!)• Camouflage ( you can’t see me!)• Mimicry (look like something scary!)• Warning Coloring (Look OBNOXIOUS!)

Alert

Skunk Spray

Camouflage

Mimicry

Warning Colors

Symbiosis

• Can’t we all just get along!• 3 Kinds:

– Mutualism (you win, I win, we ALL WIN!)– Commensalisms (I win, you come out even)– Parasitism (I win, you lose)

Ch. 21. 4 Changes in Communities

• Read story from Ecology Book• Coloring Activity

QUIZZES AND TESTS!

• KNOW HOW TO USE YOUR EQUATIONS! (I will give them to you, you need to plug things in)

• Know Your VOCABULARY!• Interpret Graphs!• Pick out Limiting Factors!• Study Guide: pg. 735 from text book. Answers

on next few slides: quiz your self before. I will not go over them with you.

Ch. 21 Study Guide Answers

• Organizing Information:• 1. direct observation• 2. indirect observation• 3. sampling• 4. mark-and-recapture studies

Reviewing Key Terms

• 1. B, 2. C, 3. B, 4. C, 5. D• 6. true• 7. false; population• 8. true• 9. false; competition• 10. false; host

• 11. Sample answer: biotic – trees, birds; abiotic – sunlight, soil

• 12. Plants and algae use the energy of sunlight to combine water and carbon dioxide to make their won food during photosynthesis. All consumers in that ecosystem feed directly o r indirectly on plants or algae.

• 13. Ecologist count the number of organisms in a small area, and then multiply by the number of units in the entire area to estimate the entire population.

• 14. Limited space may make it impossible for all members of the population to find places to breed or make nests

• 15. Any two: Camouflage – The organism blend in with its surroundings, making it difficult for predators to see. Protective covering – the organisms spines, shell or other outer covering makes it painful or difficult for predators to eat.

• 15. (continued) Warning coloring – an organism that is poisonous has bright colors to warn predators not to eat it.

• Mimicry- a harmless organism looks like another organism that predators have learned not to eat.

• False coloring – false “eyes” or other structures can food predators and scare them away.

• 16. Studying the entire population of the species usually is not possible because the population is too large or spread out.

• 17. Answers may include indirect observation (counting egg clusters), sampling (counting the number in a small area and then multiplying by the number of units in the entire area), or mark and recapture.

• 18. Organisms within a species share the same niche. Because individuals within a species are more similar, they will share many of the same advantages and disadvantages in surviving in a certain environment, which intensifies competition for the limited resources. Members of two different species may share some parts of a habitat but do not usually compete for all resources in the same way.

• 19. Primary succession; there is no soil (just rocks) present and only pioneer organisms are shown.

• 20. If birth rate > death rate, population size INCREASES. If death rate > birth rate, population side decreases. If immigration > emigration, population size increases. If immigration < emigration, population size decreases.

• 21. ask Mrs. Simpson. If you can’t graph points on a line, you haven’t been paying attention in math.

• 22. Highest: year 15; lowest: year 30• 23. Possible answer: Beginning with 15,000 deer

at the beginning of the study, the population increased steadily through year 15. From year 15 through the end of the study, the deer population declines steadily, reaching the population’s lowest point, 10,000 deer, in Year 30.

• 24. The severe winter may have killed the weak or injured deer. Food shortage during this winter also may have weakened deer or caused them to starve.

• Standardized Test Prep pg. 737• 1. C 2. H 3. A 4. F 5. B