3.6 echinoderms &3.7

• Biologie
• Middelbare school
• vwo
• Leerjaar 1

Echinoderms 

• have spiky skin 
  
• although they do have stiff plates under their skin for support. 
  
• are aquatic
• have radial symmetry
• have tube feet to move with

VERTEBRATES / INVERTEBRATES

Ask yourself:

 ''Does it have a backbone?

YES

NO

VERTEBRATE

INVERTEBRATE

I-Book pg. 10-13

sea stars

• with a mouth located in the center of the body.
• ‘spiny skinned’
  
• aquatic
  
• radial symmetry (5 equal parts)
  
• endoskeleton

=> sea star

What type of skeleton do molluscs have?

1. a kind of a shell
2. Endoskeleton
3. Hydroskeleton
4. Exoskeleton

What type of skeleton do Cnidarians have?

What do sponges do to catch food?

1. They swim after it
2. They filter water
3. They wait for it to swim by and grab it
4. They have specialized cells with electric pulses

Which of the following animals is NOT a mollusc?

1. Octopus
2. Snail
3. Starfish
4. Mussel

How do Echinoderms move around?

This animal has a ...

1. Bilateral symmetry
2. Radial symmetry
3. No symmetry

What is the symmetry of a wasp?

1. Bilateral
2. Radial
3. No symmetry

What is the symmetry of a sea star?

1. Bilateral symmetry
2. No symmetry
3. Radial symmetry
4. A and C are both possible

3.7 arthropods!

• Myriapods, 
• Crustaceans, 
• Arachnids 
• Insects

Arthropods

• Arthropods are invertebrates
• They have an exoskeleton
• They have segmented bodies and legs 
• Some of them have antennae on their heads
• Because of the exoskeleton, they cannot grow easily (since the exoskeleton does not grow)
• For this reason, they have to get rid of the exoskeleton and then develop a new, bigger one. We call this moulting or shedding

Segmented: this means that their body is divided into different parts. Most often, you can very clearly see the different parts.

Myriapods

• 10 or more pairs of legs
• Very segmented 
• Centipede has 1 pair of legs per segment, carnivores
• Millipede has 2 pairs of legs per segment, herbivores

Myria = many

Pods = legs

So, Myriapods means 'many-legged'

In Dutch, we call them 'veelpotigen'

What is the difference between centi and millipedes?

Insects

• 3 main body parts: head, thorax and abdomen
• 3 pairs of legs + 1 or 2 pairs of wings attached to thorax
• Can have antennae

Insects

Insects perform metamorphosis, which means that they have 2 stages during life:

1. Larvae or nymphs

2 Adult stage

Metamorphosis

A complete change of the body and way of life

caterpillar starts making pupa

butterfly emerges out of pupa

inside the pupa the caterpillar changes

Arachnids

• 2 main body parts
• 4 pairs of legs attached to front part
• Spiders, ticks, mites and scorpions
• Can be venomous!

Crustaceans

• Between 4 and 20 pairs of legs
• Live in water, but can come onto land (they have gills)
• Often, their legs look very different from each other (front vs back legs)

In Dutch, we call them 'Kreeftachtigen'

Insect

Myriapod

Arachnid

Crustacean

make the excersizes of 3.7

Why do we need bees? (and other insects)

• I can imagine why you would find insects annoying, creepy, or ugly
• However, they do have a very important job
• See the next video for that!