4th Grade Science
Water Cycle and the Role of Organisms
Unit 3
The Importance of Water on Earth
Water is the most abundant resource on Earth and most of life depends on it-- even us! It comes in many different forms: fog, clouds, rain, snow, oceans, rivers, ponds,...
Oceans support a variety of ecosystems and organisms, helps shape landforms, and influences climate (unit 1). Most of the Earth's water come from oceans while freshwater is found underground or in glaciers.
Rain also shapes land through erosion and provides necessary nutrients to support habitats and life.
Water Cycle
How does water from oceans and rivers turn into clouds and then turn back into running water through rain? This process takes place through the conversion of matter known as the water cycle. The simplified steps of the water cycle are below:
Evaporation
This first step in the water cycle takes place when heat from the sun turns liquid water from oceans and lakes into water vapors in the air.
Condensation
The second step happens when the water vapors from evaporation clump together into clouds. Clouds are made up of water/ice droplets.
Precipitation
The third and last step of the cycle is precipitation. Precipitation can come in many forms like rain, snow, drizzle, hail,...
Play this Water Cycle Quizizz to test your knowledge!
Energy Transfers
Energy is all around us and we will discuss 2 types: sound and light.
- Sound energy happens when objects collide and the air surrounding it gets heated to form sound
- Light energy from the Sun transfers energy to warm and heat up air, water and land
Relationships in Ecosystems
Have you ever wondered about the different roles that plants and animals play? Why do some eat plants, some eat meat and others eat both? These questions can be answered by understanding the ecosystem.
Food chains describes the order in which living things depend on others for food.
Food webs are made up of several interconnected food chains to show the relationships in ecosystems.
This picture shows a food web with different animals and plants
Different Roles within a Food Web
Producers
All energy comes from the sun and producers use light energy to grow. Most producers are plants that are the food source for herbivore and omnivore consumers.
Consumers
Consumers can be herbivores, omnivores or carnivores. They either eat producers or each other within a food web.
Decomposers
Decomposers are organisms like fungi or bacteria that turn dead producers and consumers into nutrients to promote the growth of producers.
Keystone species
A keystone species is a species in a certain ecosystem which has a big effect on the living things and environment around it. These species help control the population within a food web.
Characteristics of Ecosystems
Within a certain ecosystem, there may be bad things like pollution and the cutting of trees which negatively affect populations. Here is some vocabulary to describe these negative characteristics:
- Scarce: when population numbers or resources are lower than normal
- Extinct: when a certain species no longer exists in an ecosystem
- Overabundant: when population numbers are higher than normal and may be bad for the ecosystem
Changes within Ecosystems
In changing environments and conditions, species have to do some things differently to better live in a different world.
- Natural selection: some individuals in a species are able to do better in life (better at getting food) and live to pass on their genes
- Adaptations: changes in environment make animals and plants live differently in order to survive
- Biodiversity: different species in an ecosystem all work to help each other and if one is hurt, others are damaged as well
