Unit 3 a ch 8 s1 how populations change in size


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  • In the graph a vertebratepoikilotherm is a cold-blooded animal whose body temperature is affected by the external environment.
  • Picture 1:Creosote bushes release a chemical called terpene thru their roots that keep other plants from invading their space and stealing their nutrients. This puts other creosote bushes at an even distance from them.Picture 2: Dandelion seeds randomly float on the wind, land and germinatePicture 3: Herd animals like zebra live in clumps because resources may be clumped as well (water is not evenly distributed across the land)
  • Change in population = 13,940 - 12,481= 1,459Population before change = 12,4811459/12481 = 0.1168 x 100 = 11.7%
  • Pictures represent the rabbit overpopulation that occurred in Australia back in the 1850’s. Rabbits were released, able to reproduce all year due to mild winters, overpopulated and destroyed crops. The myxomatosis virus was introduced to the rabbit population and it greatly reduced the population.
  • Unit 3 a ch 8 s1 how populations change in size

    1. 1. Understanding Populations Ch8, Section 1: How Populations Change in Size Standards: SEV3e
    2. 2. What is a Population? O All members of a species living and reproducing together in the same place at the same time. O A population of daisies in a field in Georgia would only reproduce together. They would not reproduce with a field of daisies in Alabama.
    3. 3. What are the 3 properties of a population? 1. 2. 3. Size Density Dispersal Knowing the size, density, & dispersal of populations can help O characterize populations O predict changes within them Map of population density of indigo bunting bird
    4. 4. What are the 3 properties of a population? 1. Size- the number of species present
    5. 5. What are the 3 properties of a population? 2. Density- the number of species per unit area or volume O Ex: number of bass per m3 of water in a lake O Usually body size affects density: O The larger the body size, the lower the population density. O The smaller the body size, the higher the population density.
    6. 6. What are the 3 properties of a population? 3. Dispersal- relative distribution or arrangement of individuals in a particular space. O 3 Types: a. b. c. Even Random Clumped
    7. 7. 3 Types of Dispersal Patterns a. Even O O O b. Random O O O c. Evenly spaced Not common type of dispersal Ex: creosote bushes in desert Unpredictable spacing Most rare type of dispersal Ex: oyster larvae, dandelion seeds Clumped O O O Live in groups Most common type b/c resources are also clumped Ex: school of fish, herd of zebra
    8. 8. How does a population grow? O Organisms enter a population via birth. O Organisms leave a population via death O Natural change in population size = births - deaths
    9. 9. What is a Population’s Growth Rate (PGR)? O Change in a population over a given period of time. O Equation for PGR: O How to use the equation: First calculate change in population 1. O 2. 3. O New pop. Size – Old pop. size Next divide change in population by the original population size Multiply answer x 100 to get % If answer is positive the population grew O If answer is negative the population declined O If the answer is 0 the population did not change. In the year 2000, the population of Powder Springs was 12,481. In the year 2010, the population of Powder Springs was 13,940. How much did the population grow during this 10 year period? Use the Population Growth Rate equation to figure this out! Answer: +11.7%
    10. 10. How fast can a population grow? O Reproductive potential- maximum number of offspring that each member of the population can produce. O Usually the smaller the animal, the higher the reproductive potential. O Ex: insects, rodents, bacteria O Affected by: O How often organism reproduces in their lifetime O How early in life they start reproducing O How many offspring they produce in a single reproductive cycle (pregnancy)
    11. 11. How fast can a population grow? O If an organism reproduces when it is young, has a lot of babies in one cycle, and can have many cycles in its life then it has a HIGH reproductive potential. O Ex: Rabbits O O O O O Start breeding at 6 months and live for 7-10 years Produce 6-14 babies in one litter Gestation is 14-31 days so can have 1 litter per month. An 8 year old rabbit could produce 1,344 babies in her life. AND if she gives birth to females they will also have babies. RabbitHealth.com predicts 1 rabbit can be the progenitor of 95 million rabbits if you include all the female babies and their births.
    12. 12. What is exponential growth? O Population multiplies at fast increasing rate O Results from lack of limiting factors O If there’s plenty of food, water, shelter then unlimited number of organisms can survive. O Produces J-shaped curve on graph
    13. 13. What limits exponential growth? O Limited resources keep populations from reaching their reproductive potential and experiencing exponential growth. O Examples of limiting factors: O Food O Water O Shelter O Availability of mates O Availability of light (plants)
    14. 14. What limits exponential growth? O Limiting factors cause some animals to die and birth rates to decrease. O Populations will rise and fall around a particular population size. O This population oscillation creates an Sshaped curve on the graph. This is called logistic growth.
    15. 15. What limits exponential growth? O Populations will reach a carrying capacitymaximum population of a particular species that the ecosystem can support indefinitely O Represented by a straight line on a graph O The population of a species will oscillate around the carrying capacity. What is the carrying capacity for this population? Approximately 1.5 million organisms.
    16. 16. What limits exponential growth? O As population approaches its carrying capacity, there is competition for resources. O Organisms will compete indirectly for social dominance or for a territory to claim resources.
    17. 17. What are 2 types of population regulation? O Density Dependent limiting factors O Affected by crowded populations O Ex: food, water, disease O Plague spread faster thru cities than the country. O Density Independent limiting factors O Population size doesn’t matter, all will be affected equally O Ex: temperature fluctuations, natural disasters. Density Independent Example: Temperature has caused decrease in mosquito population
    18. 18. How do scientists estimate population size in the field? O Mark & Recapture O Species caught, tagged, r eleased, then caught again. Proportion of marked to unmarked gives estimate O Used for animals mostly
    19. 19. How do scientists estimate population size in the field? O Mark & Recapture Equation O N= mn r Where… N= estimate of population size m= number of individuals caught on first visit n= number of individuals caught on second visit r= number of marked individuals caught on 2nd visit Must assume that… - Population is closed geographically & no immigration or emigration - All organisms are equally likely to be captured - Catching & marking do not affect catchability - Each sample is random - Marks are not lost between sampling occasions
    20. 20. How do scientists estimate population size in the field? O A biologist wants to estimate the size of a population of turtles in a lake. She captures 10 turtles on her first visit to the lake, and marks their backs with paint. A week later she returns to the lake and captures 15 turtles. Five of these 15 turtles have paint on their backs, indicating that they are recaptured animals. What is the estimated size of the population? m = #originally marked = 10 n = total # caught in 2nd sample = 15 r = # caught in 2nd sample that were marked = 5 O N= mn = 10 x 15 = 30 turtles in this lake (approximate) r 5