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Basics About Population Growth (pages 530-533). The environment has a carrying capacity for every organism based on the available resourcesIf resources are abundant and readily available, then a population will show exponential growth. During exponential growth the increase in population size varie
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1. Carrying Capacity Population Growth of Duckweed
2. Basics About Population Growth(pages 530-533) The environment has a carrying capacity for every organism based on the available resources
If resources are abundant and readily available, then a population will show exponential growth
3. During exponential growth the increase in population size varies with the number of individuals present
Increase is gradual at first, but rises sharply as more individuals become part of the population
Unlimited resources allow everyone to reproduce!
4. Environmental Resistance Factors Populations will continue to grow exponentially until they come up against limiting factors or resistance factors
Resource limitations
Food, nutrients, water, sunlight
Shelter, space
Competition from other species
Predation
Waste accumulation
5. Logistic Growth In the real world resources are often limiting
The first part of the growth resembles exponential growth
But over time, the population size levels off in logistic growth at a point called the carrying capacity
6. Carrying Capacity The carrying capacity of the environment represents the maximum number of individuals of a particular species that an area can support indefinitely without degrading
7. Carrying Capacity Natural populations seldom approach carrying capacity smoothly
Or stay at the carrying capacity once reached
They usually fluctuate around the carrying capacity
Overshooting it or falling below depending on resources
8. Duckweed: Lemna minor A small, floating aquatic plant that forms a solid cover on the surface of freshwater ponds, marshes, lakes and quiet streams
Very important in the aquatic ecosystem as an essential link in the food chain.
Eaten by fish
birds (ducks, herons)
9. Shades extensive areas of a pond, reducing algae growth
Good for bioremediation projects
Ability to take out nitrogen and phosphorus from water
Useful as a water crop
as a source of food for animals and poultry
10. Structure of Duckweed Leaves and stems merge in a common structure called a frond or thallus
Has one root
Fronds have 3 veins
Air spaces help the plant to float
11. Reproduction Reproduction is asexual
Vegetative reproduction
Unlike the leaves of more ordinary plants, each duckweed frond contains buds from which more fronds may grow.
Until they mature, daughter fronds remain attach to the parent frond
Rapidly growing plants can have 3-4 attached fronds
12. How do Duckweed Survive? Autotrophic
Make their own food through photosynthesis
Require sunlight
Require nutrients
Phosphorous, nitrogen, other minerals
Need space to grow
13. Experiment:Population growth in Duckweed Each group will set up TWO flasks
Each flask has 100-200 ml pond water
Place 2 duckweed plants in one flask
Place 15 duckweed plants in the other flask
Count all thalli (leaves) greater than 2 mm as full grown.
Place labeled flasks under the grow lights in room 201
Record your data twice a week for 3-4 weeks (Create your own data table before you leave today)
14. What kind of population growth do you expect from the two different Duckweed flasks? Exponential growth
J-shaped growth curve
Logistic growth
S-shaped or sigmoidal