Transcript KS4 Introducing Biological Classification

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Introducing biological classification
Introducing life in the oceans
Evolution and relationships
How we classify living things
Summary
Introducing life in the oceans
Evolution and relationships
How we classify living things
Summary
Life is thought to have
started in the oceans,
more than 3 000 million
years ago
For most of this time,
nearly all life was in the
oceans
OCEANS
Time (in millions of years before the present)
present
Flowering plants
First fish
1000
3000
3000
Dinosaurs
Shelled fossils
Tree ferns & vertebrates
Jellyfish-like fossils
Land plants & invertebrates
First complex animals
2000
LAND
Seaweed-like plants
Single-celled plants
First bacteria
Single-celled plants
Introducing life in the oceans
Evolution and relationships
How we classify living things
Summary
Scientists use various techniques to
decide how plants and animals are
related to each other
They can then build a family tree for all
living things
Distance of relationship
Time
Multicellular
animals
Fungi
Multicellular
plants
Single-celled a
Protozoa
Bacteria
There are about 25 major groups of
animals
All of these are found in the oceans,
and most are found only in the oceans
Here, we will look at six animal groups,
which include some of the most
important and abundant types in the
oceans
First we will look at the main features
of each group, and then show how they
are related
Porifera (Sponges)
Most simple multicellular animals, comprising colonies of amoeboid and flagellated
cells. Body structure a hollow chamber, with the walls supported by silica or calcium
carbonate spicules. Feed by drawing water into the chamber and filtering out small
food particles
Coelenterates
Body radially-symmetrical, consisting of two distinct layers of cells. Gut with a single
opening, surrounded by tentacles. Tentacles bear stinging cells, used to capture or
paralyse prey. Two basic body plans – sac-like attached ‘polyps’ and umbrella-shaped
swimming ‘medusae’
Annelid worms
Body segmented, long and thin and typically round or oval in section. Most body
segments identical, separated from each other by septa. Closed blood system.
Nervous system comprising a ventral nerve cord, with an anterior ring. Each segment
may carry a single pair of bristly limbs
Arthropods
External skeleton based on chitin, often mineralised. The limbs are multi-jointed, one
pair per body segment. Bilaterally-symmetrical body typically divided into distinct
regions. Blood circulates within the body cavity. Nervous system comprising a
ventral nerve cord
Molluscs
Unsegmented body divided into visceral mass and ‘head-foot’. Head bears mouth,
foot used for locomotion. Visceral mass contains main body organs and is enclosed
within ‘mantle’, which often secretes a shell. Blood system usually open, circulating
within the body cavity
Echinoderms
Unsegmented body, with obvious five-rayed symmetry. Skin with calcareous plates and
spines. Tube-feet in skin used in locomotion. No blood system, and simple nervous
system
Vertebrates
Internal bony skeleton (cartilage in some groups) and segmented muscles. The
backbone protects a dorsal main nerve cord, which is expanded in the head for form
the brain. Well-developed blood system, with a heart with 3 or 4 chambers. Two
pairs of limbs. Teeth composed of dentine and enamel
You will have seen obvious differences
between the six groups
Some groups contained very simple
animals, other were more complex
We can build a family tree for these
groups of animals
Sponges are the most
primitive group of
multicellular animals
Coelenterates are more
complex than sponges, but still
have relatively simple body
structures
PORIFERA
(Sponges)
Molluscs, arthropods and annelids are
grouped together on this side of the tree
Vertebrates and echinoderms are
grouped together on this side
At this point, the tree branches
into the two main groupings of
complex animals
COELENTERATES
PORIFERA
(Sponges)
ARTHROPODS
ECHINODERMS
MOLLUSCS
ANNELIDS
VERTEBRATES
COELENTERATES
PORIFERA
(Sponges)
Introducing life in the oceans
Evolution and relationships
How we classify living things
Summary
The relationships on these family trees
are based on the degree of similarity
between organisms
Similarity is determined in a number of
different ways:
Body form (anatomy)
Development (embryology)
Composition of chemicals such as
proteins
Genetic sequencing
The greatest degree of similarity exists
between individuals within the same
species
We group species into larger units
based on similarity
The common starfish has the species
name Asterias rubens
Other, very similar starfish also belong
in the genus Asterias
Starfish are grouped with other echinoderms
All starfish
arephylum
grouped
together into
into the
Echinodermata
the class Asteroidea
Class: Asteroidea
(about 1600 species)
Genus: Asterias
Species: Asterias rubens
All animals are in the kingdom Animalia
Eukarya - organisms
with a cell nucleus
Kingdom: Animalia
(> 1 million species)
Phylum: Echinodermata
(about 8000 species)
Class: Asteroidea
(about 1600 species)
Genus: Asterias
Species: Asterias rubens
Introducing life in the oceans
Evolution and relationships
How we classify living things
Summary
You have seen that Life evolved and diversified in the
oceans
Living things are related by a
common ancestry
You have seen that Animals have developed complex
body plans from simple ancestors
Classification is based on
relationship
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