Evolution of the major groups Flashcards
(20 cards)
What is speciation?
- change within a lineage
- formation of new lineages
- organisms exist in discrete clusters
How did Linnaeus classify organisms?
- 2 kingdoms of organisms
- 3rd kingdom of non-organisms
- animals, plants and minerals (minerals later removed by Haeckel)
How did Whittaker classify organisms?
5 kingdoms - bacteria, protists, fungi, plants and animals
3 domains - bacteria, archaea and eucarya
Describe the kingdom plantae
- earliest land-plant fossils date back to Ordovician period
- argued that land plants evolved through coming together of green algae and a fungus –> mutualism
- more plausible that land plants evolved from a green algal ancestor in the intertidal zone
Describe the evolution of land plants
- vascular system - allowed plants to become big
- linear arrangement of liquid conducting cells - provides mechanical support
- lignin deposits
- waxy waterproofing to reduce water loss
- spores
- some terrestrial plants developed seeds
- travel assisted by animals in some groups
Why did land plants evolve?
- maximise light capture - foliage
- maximise water and nutrient capture - roots
- provide anchorage - roots
- extremes of climate
- need for water conservation
- physical defence against herbivores
Why are angiosperms the current dominant plant group?
- flourished from the cretaceous onwards
- able to diversify behind a biochemical shield
- diverse chemical armoury to defend against attack by herbivores
- tend to be faster-growing
- many have developed highly efficient pollination systems involving animals such as insects –> insects became very numerous and diverse by the tertiary
Describe the kingdom fungi
- rNA tells us they are more closely related to animals than plants
- are heterotrophic - feed on organic materially syntheised by plants
List the animalia that were around by the cambrian period
- sponges
- brachiopods
- comb jellies
- jellyfish
- molluscs
- worms
- arthropods
- other invertebrates
Describe the evolution of sponges (porifera)
- most basal of true multicellular animals
- evolved from single-celled protists
- protists resembled extant protist group choanoflagellates
- some choanoflagellates are colonial
- coloniality led to true multicellularity
- enabled more efficient food gathering
- tissue development –> sponges have one germ layer and lack true tissue organisation
List some examples of cnidaria
hydroids, jellyfish, sea anemones, corals
What allows cnidaria to develop tissue?
the endoderm
What are triploblastic animals?
- Contain an ectoderm, a mesoderm and an endoderm
- 2 groups –> protostomes and deuterostomes
What is a blastula?
- hollow ball of cells that forms in early embryonic development
What does the blastopore eventually form?
The mouth of the protostomes and the anus of the deuterostomes
Describe the difference between cleavage in protostomes and in deuterostomes
Cleavage is determinate in protostomes and indeterminate in deuterostomes –> cells’ fates are not fixed (stem cells)
Why did protostomes and deuterostomes develop bilateral symmetry?
- feeding related sense organs are best sited near the mouth
- concentration of nervous tissues best sited nearby
- mouth and sense organs best sited away from region where waste materials are expelled
What is the benefit of the mesoderm in locomotion?
The mesoderm is highly compressible - dissipated mechanical forces so little force transmitted to gut cavity
Describe the features of annelids
- fluid filled coelom - secondary cavity within mesoderm
- body is segmented - rings
- segments separated within by septa
- septa ensures pressure changes in one part of the body are not dissipated along the rest of the body
- rings’ muscles and septa improve mechanical efficiency of peristalsis
- appendages - paddles with chetae (bristles)
Describe the features of nematodes (roundworms)
- have persistent embryonic cavity (pseudocoelom)
- move by whip like movements due to contraction of longitudinal muscles working vs pseudocoelom and stiff body cuticle
- not capable of much directional control
