NSC Marine Sciences Marine Ecosystems and Ecology: 2.1 Identify the organisms repre

Question

2.1 Identify the organisms represented by pictures A, B and C below by giving the common name and the class name for EACH.

Picture A: A sea cucumber; Class: Holothuroidea

Picture B: A sea urchin; Class: Echinoidea

Picture C: A feather star; Class: Crinoidea

2.2 The diagram below shows the front end of a hagfish. Study the diagram and answer the questions that follow.

2.2.1 Which letter (A–E) indicates the nostril?
2.2.2 What is the adaptation and primary function of structures B?
2.2.3 Label D, which indicates the six large pores.
2.2.4 (a) Name the smaller pores, indicated by E, that continue all the way to the tail.
(b) How do the pores assist the hagfish to protect itself?
2.2.5 C indicates the mouth.
Explain how the hagfish ingests food.

2.3 Read the extract about sea squirts below and answer the questions that follow.

One of our closer relatives does not look a lot like us. It is effectively a tough, fluid-filled, translucent bag which filters water and feeds on microscopic particles it finds there. This week’s specimen is the sea squirt ...

Most members of the sea squirt group, the tunicates or Tunicata, spend their adult lives permanently attached to rocks and other underwater surfaces. They are not like a sponge (also called a 'sponge'), filtering their food out of another ship. One looking like a pale pear bag, they are actually quite unique and do resemble these animals. This may be surprising because they do look a lot like sponges, the fleshy skin that covers their body...

2.3.1 The author is quite correct in saying that the tunicates are closely related to ‘us’, as they are in the same phylum.
2.3.2 Draw a simple outline of a tunicate, the red bait, to illustrate why the author refers to it as a 'wet paper bag'.
Label the siphons. A heading is not required.
2.3.3 A closer study of the sea squirt shows only a few characteristics of the phylum that we as humans belong to.
State TWO defining features of the phylum that humans belong to. Also state why scientists have added sea squirts to this phylum.

2.4 Sea urchins are stenohaline, meaning that they can only tolerate a limited change in the salinity of their environment. The Breede River in the Western Cape has its mouth at the head of San Sebastian Bay. Sea urchins are known to move towards the mouth of the river during summer months, only to die off during winter when an increase in rainfall causes the river to flow more strongly.

In the years of the drought, which reached its peak in 2018, sea urchin populations increased in rock pools on islands and sites six.

At the end of 2018, a survey was done to determine the effect of salinity on sea urchin population densities in rock pools around six sites.

The map above shows the average sea urchin population densities and salinities recorded during December 2018 and July 2019.

2.4.1 Draw a chart for the July 2019 data, on the same set of axes, where a bar graph represents the average sea urchin population densities per site and a line graph shows salinities across the sites.

Use the following scale:

1 cm per sea urchin for the bar graph
1 cm per 5 ppt for the salinity line graph

2.4.2 Write a brief summary of the results obtained in the chart.

2.4.3 Discuss the aspects of sea urchins which make them stenohaline.

2.4.4 State possible reasons why not all the sea urchins die at some of the sites with lower salinities.

2.1 Identify the organisms represented by pictures A, B and C below by giving the common name and the class name for EACH - NSC Marine Sciences - Question 2 - 2021 - Paper 2

Worked Solution & Example Answer:2.1 Identify the organisms represented by pictures A, B and C below by giving the common name and the class name for EACH - NSC Marine Sciences - Question 2 - 2021 - Paper 2

Identify the organisms represented by pictures A, B and C.

Which letter (A–E) indicates the nostril?

What is the adaptation and primary function of structures B?

Label D, which indicates the six large pores.

Name the smaller pores, indicated by E, that continue all the way to the tail.

How do the pores assist the hagfish to protect itself?

Explain how the hagfish ingests food.

The author is correct in saying that the tunicates are closely related to 'us'.

Draw a simple outline of a tunicate, the red bait.

State TWO defining features of the phylum that humans belong to.

Draw a chart for the July 2019 data.

Write a brief summary of the results obtained in the chart.

Discuss the aspects of sea urchins which make them stenohaline.

State possible reasons why not all the sea urchins die at some of the sites with lower salinities.

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