P wave
the fastest seismic wave, which travels through gases, liquids, and solids; also called primary wave
Pacific Plate
lithospheric plate that consists of the Pacific Ocean and a narrow piece of California west of the North American Plate
pampas
the grasslands of Argentina and home to pampas deer.
Pangaea
Earth's single landmass, or supercontinent, that is thought to have existed about 200 million years ago
parasite
an organism that lives inside another organism and feeds off it
parent rock
the rock from which soil is formed
permafrost
the permanently frozen soil layer in the tundra biome
petrochemical
a chemical that comes from petroleum or natural gas
pH scale
scale used to measure the acidity or alkilinity of a substance
phloem
tubes within a plant stem that move food from the leaves to other parts of the plant
photosynthesis
the process of making food by using sunlight; used by plants and some other organisms
physical weathering
the process that breaks a rock apart into smaller and smaller pieces that retain the characteristics of the original rock and also known as mechanical weathering
phytoplankton
microscopic organisms that, like plants, use the Sun's energy to make food through photosynthesis
plankton
microorganisms that live near the surface of the ocean; the two types are phytoplankton and zooplankton
plastic
a synthetic substance derived from petroleum, a fossil fuel
plate tectonics
the theory that Earth's surface is made up of separate, rigid plates that move slowly across the mantle
pollution
a harmful change in the natural environment; usually the result of human activities
polymer
a chemical compound that is made of repeating parts; plastic is an example
polymerization
the process of chemically linking many smaller molecules to form a larger molecule that has different physical properties
population
all the organisms of one species in an ecosystem
potential energy
the energy stored in an object by changing its location
precipitation
any form of water_rain, snow, sleet, or hail_that falls to Earth
predator
a living thing that hunts and kills other living things for food
prey
the animals that predators hunt for food
primary consumer
an organism that eats producers and is the second link in a food chain after producers
producer
an organism, such as a plant or type of algae, that uses energy from the Sun to make its own food
product
a new substance formed from a chemical reaction
prokaryote
an organism that has a simple cell structure without a nucleus in each cell
protist
a single-celled, eukaryotic organism that cannot be clearly classified as animal or plant
protozoan
a protist that has no cell walls and can find and eat food; examples include flagellates and ciliates
pseudopod
a cell extension used by protists to move about and capture food and it means false foot.
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