NSC Marine Sciences Marine Biodiversity and Evolution: Identify the organisms represent

Question

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

A

B

C

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.

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 that spends its life sucking in water and feeding on microscopic particles it finds there. This week's specimen of the sea squirt group, the tunicates or Tunicata, spend their adult lives permanently attached to rocks and other hard underwater surfaces.

The interesting thing about tunicates is that they are closely related to another group of animals called vertebrates. Although they look like a pear-shaped bag, they are actually very closely related to fish. This may be surprising because they do not look like sponges, the closest thing to them in an evolutionary sense.

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.

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, where a few months, only to die during winter when an increase in rainfall causes river water to flow in more strongly.

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

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

In 2018, the average population density of sea urchins at all the sites was 10 sea urchins per square metre (m²).

The salinity was the same at all sites, measuring 35 ppt (parts per thousand).

Two weeks after the first significant flow of water into the bay, in July 2019, a second survey was done.

The table below shows the average sea urchin population density and salinity at each of the sites.

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 on the chart.

2.4.3 Discuss the aspects of sea urchin physiology that makes them stenohaline.

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

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: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

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.

2.2.4 (b) How do the pores assist the hagfish to protect itself?

2.2.5 Explain how the hagfish ingests food.

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

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'.

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

2.4.1 Draw a chart for the July 2019 data.

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

2.4.3 Discuss the aspects of sea urchin physiology that makes them stenohaline.

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

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