Question

predicting changes in arctic ecological communities
part 1: examining data on arctic sea ice extent
arctic sea ice, the layer of frozen seawater covering much of the arctic ocean and neighboring seas, is often referred to as earth’s air conditioner: its white surface bounces solar energy back to space, cooling the globe. the sea ice cap changes with the season, growing in the autumn and winter and shrinking in the spring and summer. its minimum summertime extent (how much surface area it covers), which typically occurs in september, has been decreasing, overall, at a rapid pace since the late 1970s due to warming temperatures.

graph: arctic sea ice minimum extent in september (1979–2017), y-axis: sea ice minimum (million km²), x-axis: year (1980, 1985, 1990, 1995, 2000, 2005, 2010, 2015, 2020)
figure. arctic sea ice minimum extent in september (1979–2017)
text and graph adapted from “end-of-summer arctic sea ice extent is eighth lowest on record.” © 2017 by nasa.

1. based on the introductory text, what does extent mean?
2. **what measurement on the graph provides evidence that surface area is being measured?
3. *what does one data point on this graph represent?
4. **predict which organisms may depend on arctic sea ice.

Explanation:

Question 1

The introductory text says "how much surface area it covers" when defining the minimum summertime extent of Arctic sea ice. So "extent" here means the surface area that the Arctic sea ice covers.

The y - axis of the graph is labeled "Sea Ice Minimum (million km²)". The unit "km²" (square kilometers) is a unit of area. Since surface area is being measured, the y - axis measurement with the unit of area (million km²) provides evidence that surface area is being measured.

The x - axis of the graph is labeled "Year" and the data points are plotted over different years (from 1980 to 2020 approximately). The y - axis is the sea ice minimum extent. So one data point on this graph represents the minimum extent (in million km²) of Arctic sea ice in September for a particular year.

Answer:

The surface area that the Arctic sea ice covers.

Question 2