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In springtime, air temperatures increase and surface ice melts. When the temperature of the surface water begins to reach 4 °C, the water becomes heavier and sinks to the bottom. The water at the bottom of the lake is then displaced by the heavier surface water and, thus, rises to the top. As that water rises to the top, the sediments and nutrients from the lake bottom are brought along with it. During the summer months, the lake water stratifies, or forms layers, with the warmest water at the lake surface.

As air temperatures drop in the fall, the temperature of the lake water cools to 4 °C; therefore, this causes fall turnover as the heavy cold water sinks and displaces the water at the bottom. The oxygen-rich water at the surface of the lake then moves to the bottom of the lake, while the nutrients at the bottom of the lake rise to the surface ( [link] ). During the winter, the oxygen at the bottom of the lake is used by decomposers and other organisms requiring oxygen, such as fish.

Temperature

Temperature affects the physiology of living things as well as the density and state of water. Temperature exerts an important influence on living things because few living things can survive at temperatures below 0 °C (32 °F) due to metabolic constraints. It is also rare for living things to survive at temperatures exceeding 45 °C (113 °F); this is a reflection of evolutionary response to typical temperatures. Enzymes are most efficient within a narrow and specific range of temperatures; enzyme degradation can occur at higher temperatures. Therefore, organisms either must maintain an internal temperature or they must inhabit an environment that will keep the body within a temperature range that supports metabolism. Some animals have adapted to enable their bodies to survive significant temperature fluctuations, such as seen in hibernation or reptilian torpor. Similarly, some bacteria are adapted to surviving in extremely hot temperatures such as geysers. Such bacteria are examples of extremophiles: organisms that thrive in extreme environments.

Temperature can limit the distribution of living things. Animals faced with temperature fluctuations may respond with adaptations, such as migration, in order to survive. Migration, the movement from one place to another, is an adaptation found in many animals, including many that inhabit seasonally cold climates. Migration solves problems related to temperature, locating food, and finding a mate. In migration, for instance, the Arctic Tern ( Sterna paradisaea ) makes a 40,000 km (24,000 mi) round trip flight each year between its feeding grounds in the southern hemisphere and its breeding grounds in the Arctic Ocean. Monarch butterflies ( Danaus plexippus ) live in the eastern United States in the warmer months and migrate to Mexico and the southern United States in the wintertime. Some species of mammals also make migratory forays. Reindeer ( Rangifer tarandus ) travel about 5,000 km (3,100 mi) each year to find food. Amphibians and reptiles are more limited in their distribution because they lack migratory ability. Not all animals that can migrate do so: migration carries risk and comes at a high energy cost.

Questions & Answers

what is matter
Emmanuel Reply
matter is anything that has mass and can occupied space
Alice
weight
Alice
how the kidney functions as osmoregulatory organ
Sam Reply
That true
Banda
what is the major connection for sugars in glycolysis?
Ibrahim Reply
Simple term of science
Palesa Reply
what does it mean
gopal
it's means what do u know about biology?
Phathu
what is immunisation
Melysa
the action of making a person immune to infections ,for immunisation
Kalia
what is the biology? what do you know about biology
Phathu Reply
biology is the study of living organisms, divided into many specialized fields that cover their morphology, physiology, anatomy, behavior, origin, and distribution.
Julia
The study of all aspects of life. The study of all living organisms (such as animal cells and plant cells) in greater detail (their structure and how they function). It's a very broad science.
juanita
what is prokaryotic
Bhaskar Reply
what is pathogens
Bhaskar
transistion metals....
Wasik Reply
Why study ecology
Amos Reply
What name is given to group 8metals on a periodic table
Amos
to know interaction of living organisms and their environment
Alice
what is evolution
Elia Reply
Is the gradual change of something it can be either organisms
Amos
which of the following statements about the moss life cycle is false?
Israel Reply
posterior lobe of pitutary contains what?
MR Reply
What if vincristine and colchicibe disrupt mitosis by binding to tubulin
Rohith Reply
A plant in the understory of a forest displays a segmented stem and slender leaves arranged in a whorl. It is probably....
Israel Reply
How did the development of a vascular system contribute to the increase in size of plants?
Israel
If a flower lacked a megasporangium and microsporangium, what type of gametes would not form?
Israel
Seed plants are.. A. all homosporous B. mostly homosporous with some heterosporous C. mostly heterosporous with some homosporous D. all heterosporous
Israel
Besides the seed, what other major structure diminishes a plant's reliance on water for reproduction?
Israel
what role did the adaptations of seed and pollen play in the development and expansion of seed plants?
Israel
Some cycads are considered endangered species and their trade is severely restricted. Customs officials stop suspected smugglers who claim that the plants in their possession are palm trees, not cycads. How would a botanist distinguish between the two types of plants?
Israel
What are the two structures that allow angiosperms to be the dominant form of plant life in most terrestrial ecosystems?
Israel
how are carbohydrates,proteins and fats formed from triose phosphate
fonyuy Reply
Why does the actin filament only move in one direction? Describe in great detail.
Lashonda Reply
Two events happen when calcium binds to troponin.
Lashonda

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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