CLEP REA Chapter 7 - Population Biology

Water cycle

water vapor circulates through the biosphere in a process called the hydrologic cycle. Water is evaporated via solar radiation from the ocean and other bodies of water into clouds. Water is also released into the atmosphere from vegetation (leaves) by transpiration. Some water is also evaporated directly from soil, but most water in the ground flows into underground aquifers, which eventually empty into the oceans. Water above ground flows into waterways, which also eventually flows into the ocean (a process known as runoff). Water vapor is then redistributed over land (and back into the oceans as well) via clouds, which release water as precipitation.

How does the water cycle affect the climate?

Clouds reflect the Sun’s radiation away from the Earth, causing cool waehter. Water vapor in the air also acts as a greenhouse gas, reflecting radiation from the Earth’s surface back towards the Earth, trapping heat. The water cycle also intersects nearly all other cycles of elements and nutrients.

Nitrogen fixing

The process of combining nitrogen with either hydrogen or oxygen, mostly by nitrogen-fixing bacteria, or to a small degree by the action of lightning.

nitrogen-fixing bacteria

they live in the soil and perform the task of combining gaseous nitrogen fro the atmosphere with hydrogen, forming ammonium (NH4+) ions. Ammonium ions are then absorbed and used by plants.

Other types of nitrogen-fixing bacteria live in symbiosis in the nodules of the roots of legumes, supplying the roots with a direct source or ammonia.

nitrates

some plants are unable to use ammonia, and use nitrates instead.

nitrification

breaking down ammonia into nitrites (NO2-). Then other bacteria convert nitrates into nitrated (NO3-)

other places that ammonia and nitrates are produces

volcanic activity, lightning.

How is nitrogen passed along the food chain?

When plants are consumed, the amino acids are recombined and used, a process that passes the nitrogen-containing molecules on the through the food web or chain. Animal waste products, such as urine, release nitrogen compounds (primarily ammonia) back into the environment. Finally, large amounts of nitrogen are returned to the Earth by bacteria and fungi, which decompose dead plant and animal matter into ammonia (and other substances) through a process known as ammonification.

denitrification

breaking down excess nitrates, which released nitrogen gas back into the air. carried out by various bacteria and fungi.

ethology

how animals and and react within their environments

taxes

directional responses either toward or away from a stimulus

kineses

changes in speed of movement in response to stimuli

reflexes

an automatic movement of a body part in response to stimuli

fixed action pattern

complex, but steretyped behaviors in response to a stimulus

FAPS includes

courtship behaviors, circadian rhythms, and feeding of young.

condioning

apply an old response to a new stimulus

habituation

where the organism produces less and less response as a stimulus is repeated, without a subsequent negative or positive action

imprinting

learned behavior that develops in a criticiar or sensitive period of the animal’s life span

home range

an area in which animnals spend most of their time

territory

an area within the home range that an animal will defend as their own

social animals tend to exhibit

altruism

demographic transition

proposes that there are progressive demographic time periods of human population growth.