Topic: Spiders and ticks

Author: Elżbieta Szedzianis

Target group

6th grade student of elementary school.

Core curriculum

6) Arthropods. Student:

a) presents the habitat, morphological features and mode of life of crustaceans, insects and arachnids,

b) observes arthropod representatives (photographs, films, diagrams) and presents the common features of this group of animals,

c) presents the significance of arthropods (including parasitic forms and pests) in nature and for humans.

Lesson objectives

Students describe the external body structure of the spider, its adaptation to the habitat and to performance of vital functions as well as a tick’s adaptations to parasitism.

The criteria for success

• you will observe the spiders and describe their body structure;

• you will specify three adaptations to the habitat and three adaptations to food intake of a spider;

• you will recognise a tick;

• you will list ways to prevent tick bites;

• you will describe the significance of arachnids in nature.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basis competences in science and technology; 

• digital competence;

• learning to learn;

• social and civic competences.

Methods/forms of work

Field classes, macroscopic observation, working using a model, “Tell your neighbour” method, “instantaneous information” method, working with text, working with film.

Individual activity, activity in pairs and activity in groups.

Teaching aids

• abstract;

• interactive whiteboard or traditional blackboard;

• computers/tablets;

• cup magnifiers;

• balloons;

• ropes;

• creative wires;

• colourful marker pens;

• hot melt glue gun;

• glue inserts.

Before classes

Students watch a presentation entitled “Kleszcze stanowią zagrożenie” (Ticks pose a risk). According to the instructions in this presentation, they prepare tick‑resistant clothing. They will wear this clothing during classes, some of which will take place outside the school building. Students should also remember to take their rucksack, a bottle of water, a notebook and a pen with them.

Lesson plan overview

Introduction

1. The teacher asks the students to choose a partner and to check his/her preparation for the trip (whether he/she has the right clothing and items).

2. The teacher reminds students the rules they have to follow outside the school building. The teacher explains the course of the classes.

Realization

1. The teacher discusses the concept of arthropods. Together with the students, the teacher analyses an interactive illustration of the spider's body structure. Then, the teacher asks the students to list the features of spiders that determine their classification as arthropods.

2. The students consolidate the acquired information by discussing it with their closest neighbours (“Tell your neighbour” method).

3. The teacher divides the students into groups of four. The teacher asks the students to disperse in groups
   no more than 100 m away and to find as many spiders and their webs as possible.
   When they find a web, they should wait for the spider to appear or shake the web gently
   to lure it out of its hiding place. The aim of this task is to demonstrate the adaptation of spiders to predation.

4. Students read the abstract entitled “The spiderweb” and write a note about spiders’ hunting.

5. Students should carefully grasp the largest spider specimens and place them into
   cup magnifiers. They look at the caught specimens and then draw a spider shape seen from above. They describe the spider’s external body structure in the drawing.

6. The teacher points out spiders with features easy to remember: flower crab spiders, cross spiders, jumping spiders.

7. The teacher presents a picture of the spider's eyes on the tablet (e.g. from the website http://www.national‑geographic.pl/media/cache/photo_view_big/uploads/media/userphoto/0003/91/716414492084cde2115a59f1f3739ff5647f9102.jpeg).

8. Students take photographs of spiders and write down their adaptations to predation.

Summary

1. On returning to the classroom, the teacher distributes balloons, ropes, creative wires and colourful marker pens to the students. Their task is to create a model of a spider from the received materials and to prove that the spider shows the features of arachnids. The teacher glues together the elements of the models prepared by the students.

2. Using the “instantaneous information” method, the students discuss risks associated with
   ticks and explain what needs to be done at home after the trip to prevent
   tick bites.

3. Students do interactive exercise no. 1 and interactive exercise no. 2. The teacher analyses the correct answers with the students.

4. The teacher displays the criteria for success and asks the students to assess their skills acquired during the classes.

Homework

On the basis of available sources, students prepare a note about the importance of arachnids in nature.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

**Crustaceans and arachnids **

Spiders, insects and crayfish belong to a large and diverse group of arthropods – animals with segmented bodies and jointed appendages. Segments of the appendages are connected to each other by joints, i.e. in a movable way. The number of walking legs ranges from six to more than a hundred. Apart from them, there are also appendages that perform other functions than locomotion. Some of them are located around the mouth (they form the oral apparatus), their role is to grasp and crush food. Other appendages – antennae are designed to receive information from the environment. Others are equipped with respiratory organs.

The body of arthropods usually has bilateral symmetry, divided into head, thorax and abdomen. In insects, the head and the thorax are separated, in crustaceans and arachnids they are immovably connected, forming a cephalothorax. The body of the arthropods is covered with a chitin cuticle, in some crustaceans additionally saturated with calcium salts, which give it high hardness. It serves as the external skeleton, is a place for the attachment of muscles, protects the internal organs against mechanical injuries and against drying out (in the case of terrestial forms).

The outer carapace prevents the arthropods from growing continuously. Therefore, they only increase in size during the moulting period. Then the old cuticle is thrown away and replaced with a new one, softer and slightly bigger than the previous one. The animal grows intensively before it hardens again.

Arthropods inhabit all living environments. They live in the air (insects), in fresh and salt water and on land.

The vast majority of crustaceans live in – salt or fresh water. Only a few are able to live on land in humid environments, especially in the tropics. Most of them have to return to the sea for breeding.

Crustaceans are arthropods whose body is usually composed of a cephalothorax and an abdomen. In the front part of the cephalothorax there are eyes placed on the posts allowing to observe the surroundings above the carapace. Below these are two pairs of antennae for receiving tactile stimuli. The crustacean cephalothorax is equipped with 5 pairs of walking legs, the first of which can be finished with claws. Abdomen appendages are usually flattened in shape and are used for swimming. They can also be used for respiration if gills are placed on them. Most crustaceans respire using gills. They may be in the form of alveoli on the thorax and abdomen appendages, but they usually fit in the gill chambers under the dorsal part of the carapace. Only in very small species the gas exchange occurs with the entire body surface.

Crustaceans include both very small organisms that live in the plankton (daphnias, cyclops and gammarids) and large organisms covered with thick and hard carapace (crayfish, crabs and lobsters). The few marine arthropods, e.g. Balanus and Lepas anatifera, belong to sedentary species, and their bodies are covered with a carapace made of calcareous plates. Crustaceans may be predators, saprophaguses, filter feeders or parasites.

Planktonic crustaceans, such as daphnia and cyclops, as well as krills forming banks are a source of nutrition for many animal species – mainly fish, birds and mammals. Predatory species such as crayfish, crabs, crawfish and lobsters regulate the number of aquatic animals, mainly molluscs, insects and their larvae as well as other crustaceans. Some crustaceans, such as crayfish, shrimps, lobsters and crawfish, are appreciated for their taste qualities and often consumed, especially in countries with access to the sea or the ocean.

Arachnids are arthropods whose body is usually composed of a cephalothorax and an abdomen. They live in various environments. The vast majority of these animals live on land. These include, for example, the spiders and Opiliones (colloquially known as harvestmen) (arachnids with a very short body and very long, thin legs) commonly occurring in Poland and scorpions with large pedipalps, resembling the crayfish pincers, found in warmer areas than ours. They respire using atmospheric air and the chitin carapace protects them against water loss.

Spiders have 4 pairs of walking legs growing out of the cephalothorax. There are no legs on the abdomen. At the front of the cephalothorax, arachnids have eyes and pedipalps. One pair of pedipalps extends beyond the contour of the head section and may look like antennae, which however do not occur in arachnids. Mouthparts are used to grab and hold the prey, crush food and act as a touch organ. The second pair of pedipalps pierces the body of a prey and introduces venom into it. It is often used to fight aggressors. On the underside of a spider's abdomen, to the rear, there are spinnerets. It is a place of spigots of silk glands producing a liquid protein substance which, after contact with air, solidifies in the form of a spider web thread. At the end of the abdomen, scorpions have a characteristic venomous sting with the use of which the predator kills the prey.

Spiders spin different types of thread. Some of them are used to build spider’s webs and safety threads, others to wrap the caught preys, and yet others to build nests and cocoons, inside of which fertilized eggs are laid. Some spiders, especially small ones, produce a thread called ballooning. On the web, which is made of these thin, long threads, its creators float in the air and move with the wind for a distance of even several hundred kilometers.

It takes time to build up webs. Usually spiders spin them at night, when they are safer. The construction starts by releasing the base thread with the wind, which adheres to a rough surface. The spider carefully passes through it and strengthens it with new threads. Then it adds another one, creating an Y‑shaped structure, and adds more rays. When they are ready, the spider connects them with sticky spiral threads or circular threads. Auxiliary threads are dry and are a pathway for the spider, and sticky threads create the right insect traps. A spider who waits in hiding, registers the vibrations of the web in which the prey has been caught with its appendages. It quickly runs up and injects venom into the caught insect which immobilizes it. Then the spider injects digestive juices into it, which turn the victim's tissues into liquid food. This process is called external digestion. Then the spider wraps its prey around with a thread and often hangs it on a spider’s web. The spider sucks in the nutrition from the prey only some time after the introduction of digestive juices.

Arachnids include ticks – ectoparasites (external parasites) that transmit severe diseases such as malaria‑like babesiosis, tick‑borne encephalitis and borreliosis. Ticks are found on the edges of deciduous and mixed forests, in glades, thickets and grasslands up to a height of 1.5 metres. They sit on the underside of the leaves, mainly at their ends or on branches near wildlife paths, from where they are collected by preys squeezing in the thicket. To avoid these parasites, one should wear long‑sleeved clothing, legwear and a headgear on a trip to the forest, change ones clothes on the return and check that there are no uninvited guests on one’s body. Sometimes it is easy to miss ticks, as their larvae can be barely 1 mm long. If it turns out that the tick has attached, remove it with a quick motion by grasping it right next to the skin. Do not grease the tick, burn it or screw it out, as when irritated it can return saliva and germs to the wound. It should be remembered that not all ticks transmit pathogenic micro‑organisms and that the risk of their injection, if the tick has been feeding for less than 24 hours, is low. Nevertheless, the place of the bite must be observed. The appearance of circular skin redness around the wound and symptoms similar to a cold: headache and limb pain, a feeling of general disintegration, fever throws require medical consultation.

Other arachnids that may be dangerous to humans are microscopic mites (Acarina) living in the house dust, bedding and mattresses. They feed on organic remains. Their faeces contribute to the occurrence of allergies with symptoms such as catarrh, cough, bronchial asthma and dermatitis.

Sarcoptes scabiei (itch mite) also belongs to the group of mites. It is about 0.4 mm long. It drills tubules in the skin, feeds on tissues, causes strong itching. It causes scabies, a very infectious disease transmitted through the direct contact.

• Arthropods are animals with segmented both bodies and appendages, the elements of which are connected by joints. Their body, covered with a chitin cuticle, is divided into a head, a thorax and an abdomen (in insects) or a cephalothorax, an abdomen (in crustaceans and arachnids) and usually 5 pairs of walking legs.

• Arachnids are arthropods that live mainly on land. They have 4 pairs of walking legs located on the cephalothorax.

• Among the arachnids there are predators weaving webs, parasites (also human parasites) and saprophytes.