Lesson 1 Flashcards
Animals have 4 features
- Multicellular
- heterotrophic
-eukaryotes - have tissue that develop from embryonic layers
Cleavage
- the zygote undergoes a succession of mitotic cell divisions (without cell growth between the divisions)
- leads to the formation of the blastula
Blastula
-after cleavage- it is a hollow mass structure in the form of a ball
-gastrulation comes after
Gastrulation
- One end of the embryo folds inwards, expands, and eventually fills the blastocoel, producing layers of embryonic tissues; the ectoderm (outer layer), and the endoderm (inner layer)
- Layers of embryonic tissues that will develop into adult body parts are produced
- Ends with a gastrula
larva
-A sexually immature form of an animal that is morphologically distinct from the adult
-usually eats different food
- may have a different habitat than the adult, as in the case of the aquatic larva of a mosquito dragonfly
Metamorphosis
Animal larvae eventually undergo metamorphosis, a developmental transformation that turns the animal into a juvenile that resembles an adult but is not yet sexually mature.
What are the 6 stages of early embryonic development in animals?
- Cleavage … (eight cell stage)
- Blastula
- Gastrulation
- Gastrula
- Larva
- Metamorphosis
What is the cavity inside the blastula called?
blastocoel
Cross section of the gastrula
- the pouch formed by gastrulation, called the archenteron, opens to the outside via the blastospore
- the endoderm of the archenteron develops into the tissue lining the animal’s digestive tract
Which animals do NOT have Hox genes?
sponges
Animal development is controlled by a similar set of ____across a broad range of taxa.
hox genes
Hox genes
regulate the formation of the posterior-anterior (front-to-back) axis, as well as other aspects of development
How many extant species of animals are identified?
1.3 million
Ediacaran biota (neoproterozoic era 1B- 542M years ago)
an early group of soft-bodied multicellular eukaryotes (dates from 560 million years ago)
earliest known macroscopic animals
Cambrian explosion
another wave of animal diversification around 535-525 million years ago, during Cambrian period of the paleozoic era
most of the fossils from the Cambrian explosion are ___.
bilaterians
bilaterians
an enormous clade whose members have a two-sided or bilaterally symmetric form and a complete digestive tract (mouth and anus).
Why is the Burgess Shale important?
This site preserved fossils from the Cambrian period.
body plan
A particular set of morphological and developmental traits integrated into a functional whole-the living animal
radial symmetry
ex: sea anemone (phylum Cnidaria)
does not have a left or right side. Any imaginary slice through the central axis divides the animal into mirror images.
Bilateral symmetry (they have brains)
ex: lobster (phylum Arthropoda)
has a left and right side. Only one imaginary cut divides the animal into mirror-image halves.
diploblastic animals- which tissues do they have (2)? And which phyla (1)?
Cnidarians and a few other animal groups that only have the ectoderm and endoderm
Triploblastic
Having a mesoderm. Most bilaterally symmetrical animals are triploblastic. ex vertebrates, arthropods, and flatworms.
mesoderm
forms the muscles and most other organs between the digestive tract and the outer covering of the animal