adaptation 16 Flashcards
Characteristics of deuterostomes
- phyla?
- Radial cleavage
- Coelom
- mouth forms (second) at opposite end of embryo to blastopore
Echinoderms
Hemichordates
Chordates
Characteristics of echinoderms? Adaptations? give examples
- exclusively marine
e. g. star fish, sea cucumbers, sea cucumbers - bilateral symmetry in larva
- pentaradial symmetry in adult
- internal calcified plates form “skeleton” (support system)
Water vascular system, part of coelom, ending in multitude of tube feet
- locomotion + foraging
- gas exchange
- nutrient/waste transport
- excretion
Characteristics of hemichordates? Adaptations? give examples
- worm-like marine deuterostomes
3 main body parts
- proboscis
- collar, with mouth
- trunk
e. g. acorn worms
- live in burrows/ muddy sediments
- capture food with sticky, mucus covered proboscis
- cilia move food particles to mouth
- respiration through large number of pharyngeal gills
Defining features of chordates
clades?
at at least some stage in develop
- a hollow dorsal nerve cord
- tail that extends beyond the anus
- a dorsal supporting rod called the notochord
Clades
- Urochordates (tunicates)
- Cephalochordates
- Vertebrates
Adaptations of Cephalochordates?
marine
- retain all defining features of chordates
- filter feeders (using pharyngeal basket)
Adaptations of urochordates (tunicates)? Clades?
Tunicates
- all marine filter feeders (pharyngeal basket)
- many form colonies
Adults lack most chordate filters
only animals that can synthesise cellulose (forms ‘tunic’ = bag-like body)
3 major clades
- Ascidians (sea squirts)
- Thaliaceans (salps)
- Larvaceans (form mucus nets to ensnare plankton prey)
Main innovations in vertebrate evolution
- key features
Vertebrates arose in marine/estuarine waters
- subsequently colonised land, fresh water
Key change: notochord replaced with a jointed vertebral column
- supported evolution of large and active bodies
- Anterior skull with large brain
- rigid internal skeleton supported by vertebral column
- internal organs suspended in coelom
- well developed circulatory system with ventral heart
Main groups of vertebrates?
3 main groups
Jawless fish
- Hagfish
- Lampreys
Jawed fishes
- cartilaginous fish
- ray-finned fishes
- lobe-finned fishes
- lungfishes
Tetrapods
Jawless fish types and adaptations
Hagfish ‘slime-eels’
- partially formed cranium, no vertebral column
- weak circulation
- eat rotting flesh, produce copious slime
Lampreys
- complete cranium and seperate vertebrae
- adults ectoparasitic (sucker + raspy teeth)
- Ammocoete larvae filter-feed before becoming parasitic
Characteristics of cartilaginous fish?
- examples
- paired median and caudal fins stabilise swimming
- skeleton composed of firm cartilage
- flexibly leathery skin with placoid scales
- mostly predators
- mostly marine (some freshwater)
e. g. sharks, rays
Characteristics of ray-finned fish?
- examples
Large, diverse group (majority of fish)
- fins with bony fin rays
- calcified, bony skeleton
- embedded lightweight scales in skin
- Swim bladder (for buoyancy control)
- gills open into single chamber covered by bony operculum
Complex behaviours
e.g. tuna, salmon, mackerel
Importance of lobe-finned fish and lungfish?
Lobe-finned
- 2 pairs of muscular jointed fins (became legs in tetrapod evolution)
- cartilage skeleton, but derived ancestors had bony skeleton
Lungfish
- breath air using true lungs
- closely resemble earliest tetrapods
