ks4 introducing biological classification (ppt)
TRANSCRIPT
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Introducing biological classification
Introducing life in the oceans
Evolution and relationships
Summary
How we classify living things
Introducing life in the oceans
Evolution and relationships
Summary
How we classify living things
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
Tim
e (i
n m
illio
ns o
f yea
rs b
efor
e th
e pr
esen
t)
3000
2000
1000
presentOCEANS LAND
First bacteriaSingle-celled plants
Seaweed-like plants
First complex animals
Jellyfish-like fossils
Shelled fossils
First fish
Single-celled plants
Land plants & invertebrates
Tree ferns & vertebrates
Dinosaurs
Flowering plants
3000
Introducing life in the oceans
Evolution and relationships
Summary
How we classify living things
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
Tim
e
Distance of relationship
Bact
eria Pr
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oa Si
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-cel
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Mul
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ar p
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Mul
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Fung
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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
groupsSome 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
PORIFERA (Sponges)
Coelenterates are more complex than sponges, but still have relatively simple body structures
At this point, the tree branches into the two
main groupings of complex animals
PORIFERA (Sponges)
COELENTERATES
Molluscs, arthropods and annelids are grouped together on this side of the tree Vertebrates and echinoderms are
grouped together on this side
PORIFERA (Sponges)
COELENTERATES
VERTEBRATES
ECHINODERMS
ANNELIDS
ARTHROPODS
MOLLUSCS
Introducing life in the oceans
Evolution and relationships
Summary
How we classify living things
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 proteinsGenetic 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
rubensOther, very similar starfish also belong in the genus
Asterias
All starfish are grouped together into the class Asteroidea
Genus: Asterias
Species: Asterias rubens
Class: Asteroidea(about 1600 species)
Starfish are grouped with other echinoderms into the phylum
Echinodermata
All animals are in the kingdom Animalia
Genus: Asterias
Species: Asterias rubens
Class: Asteroidea(about 1600 species)
Phylum: Echinodermata(about 8000 species)
Kingdom: Animalia(> 1 million species)
Eukarya - organisms with a cell nucleus
Introducing life in the oceans
Evolution and relationships
Summary
How we classify living things
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
You have seen that -
NOTES for USERS
The material in this slide show is designed to support the teaching of science at Key Stage 1
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