Science - Biology (last unit)

what does Turbidity mean?

• the cloudiness of water caused by large numbers of individual particles

• smell of water

• water temperature

• rate of flow in a river

why is sunlight important for a river ecosystem?

• producers in the river (plants and algae) need sunlight to produce energy via photosynthesis and pass it on to consumers

• it's very beautiful to watch sunsets by the river

• the river ecosystem doesn't actually need sunlight

Answer explanation

what can cause turbidity in river water? choose 3 correct options

• turbidity increases with the depth of water

• erosion and silt washing down

• overgrowth of algae from nutrient pollution (i.e. too much nutrients from fertilizers or sewage washing into the river)

• large fish species

• fishing rods

Answer explanation

what happens to producers in the river (plants and algae) as turbidity increases. Choose 2 correct answers

• they produce more energy and the entire ecosystem thrives

• it is more difficult for the deeper aquatic plants to do photosynthesis and they may die

• algaes actually like when it's dark and they will grow faster

• algaes will have less sunlight, there will be less energy for consumers and the whole food chain can collapse

Answer explanation

what happens to oxygen in the water as the temperature goes down?

• more oxygen can dissolve in the water

• less oxygen can dissolve in the water

• the oxygen level doesn't change because of the water temperature

Answer explanation

The temperature of the water is one of the main abiotic factors that influences the amount of oxygen dissolved in the water. The cooler the temperature, the more oxygen can dissolve into the water. The warmer the water gets, less and less oxygen can stay dissolved in the water, and the aquatic animals that use the dissolved oxygen to breathe may die.

what happens to oxygen in the water as the temperature goes up?

• more oxygen gets dissolved in the water

• less oxygen gets dissolved in the water

• the oxygen level doesn't depend on the water temperature

Answer explanation

The temperature of the water is one of the main abiotic factors that influences the amount of oxygen dissolved in the water. The cooler the temperature, the more oxygen can dissolve into the water. The warmer the water gets, less and less oxygen can stay dissolved in the water, and the aquatic animals that use the dissolved oxygen to breathe may die.

what factors determine the rate of flow of a river? select 2 correct answers.

• depth of river

• water temperature

• volume of water upstream

• turbidity

• number of fish living in the river

Answer explanation

The speed of the current depends on many things such as the depth of the water, wind, the volume of water from upstream, and shape of the river bed. The rate of flow in turn is a key factor in the type of ecosystem that is found in the river. It affects the types of species found in the river, and combined with other factors affects the amount of oxygen and nutrients.  Generally speaking, as the rate of flow decreases, dissolved oxygen also decreases because the river is warmer and less aerated; and the amount of dissolved nutrients increases because nutrients are not as ‘diluted’ by the river or not carried away as quickly and the river becomes more marsh-like. 

what factors determine the rate of flow of a river? select 2 correct answers.

• shape of the river bed

• amount of sunlight the river gets

• wind

• amount of algae

• number of bridges across the river

Answer explanation

The speed of the current depends on many things such as the depth of the water, wind, the volume of water from upstream, and shape of the river bed. The rate of flow in turn is a key factor in the type of ecosystem that is found in the river. It affects the types of species found in the river, and combined with other factors affects the amount of oxygen and nutrients.  Generally speaking, as the rate of flow decreases, dissolved oxygen also decreases because the river is warmer and less aerated; and the amount of dissolved nutrients increases because nutrients are not as ‘diluted’ by the river or not carried away as quickly and the river becomes more marsh-like. 

based on the shape of the river bed, which of these two rivers has a faster rate of flow?

Answer explanation

what impact does the slow rate of flow have on oxygen and nutrients in water? select 3 correct answers.

• the water temperature stays cooler

• the water temperature gets warmer

• there will be more oxygen

• there will be less oxygen

• the amount of nutrients will increase

Answer explanation

Generally speaking, as the rate of flow decreases:

1) dissolved oxygen also decreases because the river is warmer and less aerated

2) and the amount of dissolved nutrients increases because nutrients are not as ‘diluted’ by the river or not carried away as quickly and the river becomes more marsh-like.