This document provides an overview of vertebrates, including their key characteristics and how they are classified. It discusses the main groups of vertebrates - fish, amphibians, reptiles, birds and mammals. For each group, it describes physical features, temperature regulation, reproduction methods, and examples of common types. The largest sections are devoted to fish, amphibians, and reptiles, explaining their distinguishing attributes and subgroups in detail.

1. Unit 6
Vertebrates
Biology and Geology
1º ESO

2. Index
1. Introduction
2. Fish
3. Amphibians
3.1. Anurans
3.2. Urodeles
4. Reptiles
4.1 Chelonians
4.2. Saurians
4.3. Ophidians
4.4. Crocodilians
5. Birds
6. Mammals
6.1 Monotremes
4.2. Marsupials
4.3. Placentals

3. 1Introduction
Characteristics of vertebrates
Vertebrates are animals with external bilateral
symmetry. Their bodies have two equal halves,
except for the location of the internal organs.
They have an internal skeleton, which is
made up of cartilage or bone or both, and
gives them greater flexibility and strength.
The spinal column (spine), which protects the spinal cord,
comprises several bones arranged over each other (vertebrae)

4. 1Introduction
Characteristics of vertebrates
Vertebrates also have limbs.
Vertebrates are grouped into fish or tetrapods (four-
legged animals) according to the type of limbs they have.
Tetrapods

5. 1Introduction
Characteristics of vertebrates
The body of vertebrates is divided into: Head, torso and limbs.

6. 1Introduction
Regulation of body temperature
Animals have different ways of regulating their body temperatures,
as well as different sources of body heat.
Depending on how they regulate their temperature, animals are
classified as:
 Poikilotherms: animals whose temperature changes depending
on the environmental temperature. In other words, they have a
body temperature similar to that of their environment. Fish,
amphibians, and reptiles are poikilotherms. They are also
known as cold-blooded animals.
 Homeotherms: They maintain their body temperature constant,
regardless of the environmental temperature. Birds and
mammals are homeotherms. They are also known as warm-
blooded animals.

7. Animals can also be divided by another classification system based
on whether their heat primarily comes from an external source or
an internal source.
1Introduction
Regulation of body temperature
 Ectotherms: Animals that receive heat primarily from external
sources (reptiles, amphibians, and fish).
 Endotherms: Animals that create their own heat (mammals
and birds).

8. 1Introduction
Regulation of body temperature
These two systems overlap. Homeotherms can also usually be
classified as endotherms, and poikilotherms can usually be
classified as ectotherms. However, these rules aren’t always true.

9. 1Introduction
When did vertebrates first appear?
The first vertebrates on Earth were aquatic animals like fish,
which evolved into amphibians and reptiles. Reptiles evolved into
birds and mammals.
https://www.youtube.com/watch?time_contin
ue=175&v=OdhPIfOgwAo&feature=emb_logo

10. 2Fish

11. 2Fish
Fish are exclusively aquatic vertebrates; all their characteristics
make them specifically suited for living in water.
• Fish have streamlined bodies (body
shape that offers minimum resistance)
that allow them to move easily in water.
• The majority of them have protective
scales covering their bodies, that help
them glide (“planear”) in water.
• They have different types of fines to
propel themselves forward and
manoeuvre (“maniobrar”) in the water.

12. 2Fish
• They are ectothermic and most poikilotherms, in other
words, their body temperature depends on the temperature
of their environment.
• They breathe through gills.
• They have a unique sense organ called the lateral line (it
detects vibrations in water), which helps fish to navigate,
find food and avoid predator.

13. 2Fish
Nutrition
• Most fish are carnivores: some are predators, while
others are scavengers (they eat dead animals).
• There are also herbivores (they eat aquatic plants or
algae) and omnivores.

14. 2Fish
Type of fish
Bony fish Cartilaginous fish
• Bone skeleton
• Gills protected by a hard
covering (operculum)
• Mouth at the end or edge of
their head
• Homocercal tail fin (divided
into two equal parts
• Flat, round scales
• Almost all have a swim bladder
• Skeleton of cartilage
• Gills without operculum
• Ventral mouth (on or toward
the lower, abdominal plan)
• Heterocercal tail fin (divided
into two parts of different sizes)
• Thick, tooth-like scales
• Not have swim bladder.

15. Activity
Print and complete
the following
activities
Link descarga en el blog

16. 2Fish
The swim bladder is an internal gas-filled organ that
contributes to the ability of many bony fish (but
not cartilaginous fish) to control their buoyancy (“flotabilidad”),
and thus to stay at their current water depth without having
to waste energy in swimming.

17. 2Fish
Trout
Salmon
Hake (merluza)
Sharks
Skates /Rays
Type of fish
https://www.youtube.com
/watch?v=TJN3gJoZqlY

18. 2Fish
Type of fish
https://www.youtube.com/watch?v=hs2kbXUB6Q0

19. Copy and complete the following table

20. 2Fish
Reproduction
 Bony fish
Bony fish reproduce by
external fertilisation.
They are oviparous and can lay millions of eggs at a time.
This increases the chance of survival of the fry (baby fish)
as they are often eaten by their parents or other animals.

21. 2Fish
Reproduction
 Cartilaginous fish
Cartilaginous fish, such as sharks and skates, reproduce by
internal fertilisation. The males have reproductive organs
called claspers, which are used to deposit sperm in the
female´s cloaca.
Most embryonic development is
ovoviviparous in sharks and
oviparous in skates.

22. 3Amphibians

23. 3Amphibians
Amphibians are generally terrestrial vertebrates that
need to live near water or in very damp environments,
in order to avoid their skin gets dry and because they
need water to reproduce.
They are the most primitive of tetrapods and have
characteristics somewhere between fish and reptiles.

24. This skin contains many
glands that produce
substances to keep it moist
and stop it from drying out.
In some species, these glands produce venom.
They have very thin skin without scales.
3Amphibians

25. 3Amphibians
Most amphibians have four legs which them use to move
about on land and to swim.
The front legs have four toes and the back legs have five
toes, connected by membranes to facilitate swimming.

26. 3Amphibians
They are ectothermic (their body temperature depends on
the temperature of their environment), so they cannot live
in very cold places.
Adult amphibians have pulmonary and
cutaneous respiration.
The larvae breathe through gills.
Adult amphibians are carnivores. (feed on small
invertebrates that they capture with their long, sticky
tongue). The larva of some species are omnivores.
https://www.youtu
be.com/watch?v=M
FlHHG57V2U

27. 3Amphibians
https://www.youtube.com/watch?time_contin
ue=7&v=4OZJ5DmSTMg&feature=emb_logo
https://www.youtube.com/watch?v=ocfDnDVP
Gio
https://bicheando.net/2018/02/guia-sonora-del-
canto-de-los-anfibios-de-la-peninsula-iberica/
Guía sonora del canto de los
anfibios de la Península Ibérica
Watch it only if you are curious (or if you get bored a lot)

28. 3Amphibians
3.1 Anurans (frogs and toads)
They have a short body without a tail in their adult
state.
In some species, the toes on the hind feet
are joined together by interdigital
webbing to aid swimming.
Their hind legs are longer than
the front legs because they have
become adapted for jumping.

29. 3Amphibians
3.1 Anurans (frogs and toads)

30. 3Amphibians
Anurans reproduce by external fertilisation and are oviparous.
The male holds the female and releases
sperm over the ova as the female expels
then into water.
3.1 Anurans (frogs and toads)
The larvae look like fish and have external gills. They are
called tadpoles and change into adults through
metamorphosis.

31. 3Amphibians
3.1 Anurans (frogs and toads)
https://www.youtube.com/watch?v=AMs3waaW75g
https://www.youtube.com/watch?v=OZYal35e1aM

32. https://www.youtube.com/wat
ch?v=rVAjUSLkDLo
3Amphibians
3.1 Anurans (frogs and toads)
What is the difference between frogs and toads?

33. 3Amphibians
3.1 Anurans (frogs and toads)
Anuros ibéricos. Las especies de ranas y sapos.
https://www.youtube.com/watch?v=uzS8S5c7buU
Watch it only if you are curious (or if you get bored a lot)

34. 3Amphibians
3.2 Urodeles (Newts and salamanders)
Newts (tritones) Salamanders
They have a long body with a tail.
Their four legs are short and they are all the same
length.

35. 3Amphibians
3.2 Urodeles (Newts and salamanders)
Urodeles reproduce by internal fertilisation and are
oviparous.
They perform a complicated wedding dance during which
the male releases sperm in jelly-like capsules called
spermatophores, which the female then puts in her cloaca.
https://www.youtube.com/watch?v=rFO9cxf421Q
https://www.youtube.com/watch?v=5QkRScsL4Rc

36. 3Amphibians
3.2 Urodeles (Newts and salamanders)
A few days after fertilisation, the eggs are laid.
After a few weeks of being attached to an
aquatic plant, the larvae are born.
Larvae breathe through gills until they develops
lungs.
https://www.youtube.com/watch?v
=nBeo_gRDaI4

37. 3Amphibians
3.2 Urodeles (Newts and salamanders)
https://www.youtube.com/w
atch?v=hwIz-0mtIhM
Tritones ibéricos. Las especies de
la Península Ibérica.
https://www.youtube.com/watch
?v=c4V7CtB5_ac
Salamandras ibéricas. Las 9
subespecies de la Península Ibérica.
Watch it only if you are curious (or if you get bored a lot)

38. 4Reptiles

39. 4Reptiles
Reptiles are generally terrestrial vertebrates which, in
many cases, move by crawling or slithering (dragging
themselves along the ground)
https://www.youtube.co
m/watch?v=zEto1-ZTbd4
https://www.youtube.co
m/watch?v=Co7bJlJliEs
https://www.youtube.com/
watch?v=tTlLalGLvy0
https://www.youtube.com/
watch?v=joR4OL_mQnE

40. 4Reptiles
They have thick skin, without glands, which is covered
in impermeable, hard scales that prevent the loss of
water.

41. 4Reptiles
Most of them have four legs ending in five toes with
claws.

42. 4Reptiles
They are poikilothermic (ectothermic) animals.
At low temperature, they are slow and
less active, and need to warm
themselves in the sun.
They become lethargic (without
energy) in winter and they hibernate.
They have pulmonary respiration.

43. 4Reptiles
Most of them are carnivores. Some of them, like
snakes, swallow their prey whole.
Only a few, such as tortoises, and some
lizards and iguanas are herbivores.

44. 4Reptiles
Reptiles reproduce by internal fertilisation.
Almost all of them are oviparous. Their eggs
have a protective, impermeable shell and
contain nutritious substances to developing
embryo.
After fertilisation, female deposit their
eggs in the ground and abandon them,
except crocodiles, which guard their eggs
to protect them.

45. 4Reptiles

46. 4Reptiles
Groups of reptiles
Present- day reptiles are remnants of those that existed
in the past.
Reptiles can be:
• Chelonians (turtles and tortoises)
• Saurians (Lizards, geckos, chameleons and iguanas)
• Ophidians (snakes)
• Crocodilians (crocodiles and alligators)

47. 4Reptiles
4.1 Chelonians (turtles and tortoises)
They can be aquatic or terrestrial.
They have a shell which covers their trunk.
They do not have any teeth: their mandibles
form a horn-shaped beak which they use to
cut their food.

48. 4Reptiles
4.1 Chelonians (turtles and tortoises)
https://www.youtube.com/wat
ch?time_continue=14&v=Qr0xI
WECtyY&feature=emb_logo

49. 4Reptiles
4.2 Saurians (Lizards, geckos, chameleons and iguanas)
Lizards Geckos Iguanas Chameleons
They are characterised by their forked tongue (branching in
two) and the fact they regularly moult (change their layer of
scales).
Forked tongue
moulting

50. 4Reptiles
4.2 Saurians (Lizards, geckos, chameleons and iguanas)
They are mostly terrestrial.
They have a triangular head, eyes with moving eyelids and a
long torso and tail.
Some can shed their tail to distract predators,
giving them time to scape, and then grow it
back later.

51. 4Reptiles
4.3 Ophidians (Snakes)
They are characterised by their forked tongue (branching in
two) and the fact they regularly moult (change their layer of
scales).

52. 4Reptiles
4.3 Ophidians (Snakes)
They can be terrestrial or aquatic.
They have a very long body and no legs.
Their jaws allow them to swallow large prey.
Some snakes have a venomous bite.

53. 4Reptiles
4.4 Crocodilians (crocodiles, caimans, alligators and gharials)
They live in water and on land.
They are large and have large scales.
They are predators and have powerful jaws with sharp,
strong teeth.

54. 4Reptiles
4.4 Crocodilians (crocodiles, caimans, alligators and gharials)
Crocodiles Caimans
Alligators Gharials

55. https://www.youtube.com/watch?v=DefLKnKyQfA
4Reptiles
https://www.youtube.com/watch?v=l9CsBSPR14c
https://www.youtube.com/watch?v=ioblgpA5eTo
Chameleon Changing Color
https://www.youtube.com/watch?v=3kAs5yoHhF8
Reptiles general characteristics