Ecosystems are communities of abiotic and biotic components that interact together in the same environment. Ecosystems are controlled by both internal and external factors. Internal factors that control ecosystems include the availability of limiting resources, species presence, and disturbance.

Ecosystems are communities of abiotic and biotic components that interact together in the same environment. Ecosystems are controlled by both internal and external factors. External factors that impact ecosystems include but are not limited to the invasion of non-native species, climate, and time.

Despite their relatively small abundance, keystone species have a large impact on the environment in which they inhabit. If a keystone species is removed from an ecosystem, then there may be a large change in ecosystem’s stability.

Deforestation can be defined as the removal of forests by humans. Deforestation has many negative environmental impacts including soil erosion, a decline in biodiversity, and an increase in greenhouse gas emissions.

Tropical rainforest biomes have the greatest biodiversity of all biomes. They have only two seasons (rainy and dry) and the soil in these environments is generally nutrient-poor. Tropical rainforests also have a multi-layered canopy that allows little light to penetrate to the ground.

Endothermic organisms can regulate their own body temperature via internal regulation mechanisms independent of environmental factors. For example, a dog is able to cool itself down in the heat of day by panting. Exothermic organisms cannot internally regulate their own body temperature. Rather, they have external regulation, and they depend on environmental factors. The lizard mentioned cannot regulate his own body temperature. In order to warm up, he must find sunlight and heat to increase his body temperature; in order to cool down he may find shade or seek refuge underground. Exothermic organisms are extremely dependent on climate to carry out life functions. 

The principle of allocation, in regards to energy, states that energy spent doing one activity takes away the energy that could be spent doing other activities. For example, if an organism expends energy chasing prey, the organism will be tired and will have less energy to carry out other functions. 

The Second Law of Thermodynamics states that during an reaction that some energy will not be completely transferred and will ultimately be lost as heat to increase the entropy of the universe.

Endotherms regulate their body temperature, keeping it within a narrow range. To do this, they require a large amount of energy (food), more than exotherms which do not regulate their own body temperature and thus have a lower energy requirement.

Ectotherms do not regulate their body temperature; their body temperature fluctuates due to their external environment.