1.2 Terrestrial Biomes

A biome is a geographic region that is characterized by a certain climate and diverse presence of plants and animals. Due to our planet's tilt, energy from the Sun is allocated differently (most concentrated at the equator and least concentrated at the poles). Biomes are bigger than ecosystems -- a biome describes an entire ecosystem on Earth, whereas there can be many different ecosystems within that biome -- and reflect patterns of solar energy on biome maps such as the one seen below.

Terrestrial biomes are any biomes that exist on land. They are usually characterized by plant growth, temperature, and precipitation.  Aquatic biomes are biomes that are characterized by the presence of water. Divided into two main categories, marine and freshwater, they are characterized by salinity, temperature, oxygen levels, nutrient levels, and amount of light.

Tundra  The tundra is one of the coldest biomes on Earth, with average winter temperatures ranging from -40 to -10 degrees Fahrenheit (-40 to -23 degrees Celsius). It gets less than 10 inches of rain per year, relying instead on snow for present moisture. Trees cannot grow in these conditions, and are instead replaced by mosses and other small, low-growing plants. It is home to a unique community of plants and animals (moss and lichen, polar bears and Arctic foxes) adapted to survive in these harsh conditions. Additionally, the tundra is home to permafrost, a part of the ground around 3 feet deep that remains permanently frozen.

The boreal forest (also known as the taiga) is a large, coniferous forest biome found in the high latitudes of the Northern Hemisphere, including parts of North America, Europe, and Asia. The boreal forest is characterized by long, cold winters and short, cool summers, with average winter temperatures ranging from -30 to 10 degrees Fahrenheit (-34 to -12 degrees Celsius). It is home to tall trees with dense leaves that form canopies which cover the ground below. The taiga is often regarded as the second coldest global biome.

Temperate rainforests are a coastal biome that has moderate temperatures and high precipitation, often found between 30 to 50 degrees latitude in both hemispheres. Temperate rainforests aren’t very common, but do contain the most species diversification of any biome. Average annual temperatures in temperate rainforests typically range from 40 to 70 degrees Fahrenheit (4 to 21 degrees Celsius). Proximity to the oceans and equators create unique conditions, also including mainly coniferous trees. The soil is low in nutrients due to frequent rainfall, although it is better than the tundra and boreal forest. 

Found in Southern California, Australia, and South America, shrubland biomes are unique, with a 12-month growing season. Hot and dry summers combined with rainy winters create weather extremes such as droughts and wildfires. This abiotic factor necessitates that species that live here must have drought-resistant evolutionary traits.

The tropical rainforest biome is a warm and wet biome that lies near the equator. It experiences little seasonal temperature variation, often staying hot and humid, and receives a large amount of precipitation. The soil in this biome is also nutrient-poor. Unfortunately, because the ecosystem is very productive, a large portion of rainforest is cut down each year to make room for agriculture. The tropical rainforest has the most biodiversity of all the biomes. It has three distinct layers of vegetation: a canopy, subcanopy, and the forest floor.

With varying levels of precipitation, savannas are home to dry and hot seasons with few green trees or plants. This biome is often found in sub-Saharan Africa. Even though the warm temperatures promote decomposition which leads to rich soil composition, the dry climate prevents many large plants from growing. The savanna experiences hot spells much akin to those of other tropical regions, just without enough rainfall to sustain lush plant growth. Nonetheless, biodiversity in savannas is high.

The subtropical desert biome is very hot and very dry. Including the Mojave Desert, Sahara Desert, Arabian Desert, and the Great Victoria Desert. this biome homes almost no nutrients and, as a result, very little biodiversity. Plants found here include cacti plants and succulents, which are able to retain what little moisture the desert receives. Precipitation can be as low as one inch in parts.

Since there are a lot of biomes, it can be difficult to remember all of them. There are a few ways you can group them in order to remember them better. 

Biomes are generally characterized by both temperature and humidity: 

🎥 To learn more about biomes, watch this stream.