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Chapter 1-2 Science

6th Grade Study Cards

TermDefinition
1. Direct Observation 2. Indirect Observation 3. Sampling 4. Mark-and-Recapture Studies How do ecologists determine the size of a population?
Births and Deaths What causes populations to change in size?
100 X 50=5000 square meters X 20 oysters=100,000 oysters (L X W) X # of oysters in 1 square meter An oyster bed is 100 meters long and 50 meters wide. In one square meter area you count 20 oysters. Estimate the population.
join; leave Populations can change in size when new members ________ the population or when members _______ the population.
Limiting Factors What factors limit population growth?
1. Food and water 2. Space 3. Carrying Capacity 4. Weather conditions Examples of limiting factors
Population density = Number of individuals ____________________ Unit area Formula for population density
population density The number of individuals in an area of a specific size.
100 worms per square meter 500 worms/5 square meters There are 500 worms in a garden measuring 5 square meters. What is the population density?
1. # of flamingos /L X W = Area 20 flamingos/4 X 2 = 8 meters 20 flamingos/8 meters = 2.5 flamingoes per square meter is the population density Suppose you have an area that in 4 meters long and 2 meters wide with a population of 20 flamingos. What is the population density per square meter?
limiting factor ________________ is an environmental factor that causes a population to decrease.
carrying capacity The largest population that an area can support.
habitat A population usually stays near its carrying capacity because of the limiting factors in its ___________.
Food as a Limiting Factor (competition) When jackals are fighting over the limited food available to them. This is an example of _________.
1. Freezing rain on an orange crop 2. A Hurricane can wash away nests and burrows Name an example of Weather as a Limiting factor
Direct Observation To count all the members of a population
Indirect Observation To calculate population of an area by observing signs of organisms rather than the organisms themselves.
Indirect Observation You have 20 trees in your back yard. Each tree has 5 nests with an average family of four birds. So each tree is home to about 20 birds. You can multiply 20 birds by the number of trees (20) to get an answer of 400 birds.
Sampling One way to estimate the size of a population is to count the number of organisms in a small area (a sample), and then multiply to find the number in a larger area.
estimate An approximation of a number, based on reasonable assumptions.
Sampling To estimate the birch tree population in a forest, count the birches in a small area. Then multiply to find the number in the larger area.
Mark-and-Recapture Studies Scientists capture a particular animal and mark them and then release them. Two weeks later in the same area they recapture the same animals and tally how many have marks and how many don't. Then they use a mathematical formula to estimate the population.
birth rate the number of births in a population in a certain amount of time.
death rate the number of deaths in a population in a certain amount of time.
population statement birth rate > death rate, population size increases death rate> birth rate, population size decreases
immigration moving into a population
emigration means leaving a population
emigration Food is scare so part of an antelope herd may wander off in search of better grassland. They then become permanently separated. This is an example of ______________.
Space _____________is a limiting factor for population. Example: Branches from other trees may block the sunlight the seedlings need. Some of the seedlings then die, limiting the size of the pine population.
Created by: dsimmons