Animal Diversity Flashcards
(44 cards)
What group do animals belong to?
Opisthokonta, which also includes fungi and choanoflagellates.
What is the colonial flagellate hypothesis?
It suggests that multicellularity in animals evolved from colonial choanoflagellate-like ancestors, where individual cells specialized over time, leading to true multicellularity.
Who are the closest living relatives to animals?
Choanoflagellates, modern single-celled organisms that resemble the common ancestor of animals.
What are the key characteristics that define animals? (6)
Heterotrophic, no cell wall, complex tissues, motility, diplontic life cycle, and embryonic development.
What is a diplontic life cycle?
A life cycle dominated by the diploid stage, unlike fungi (haplontic) or some algae (alternation of generations).
What is the process of embryonic development in animals? (3)
Cleavage, gastrulation, and organogenesis.
What is the main characteristic of Porifera (sponges)? (3)
They are the simplest animals, lacking true tissues and organs, and rely on water flow for feeding (filter feeders).
What are Placozoa?
Small, flat, amoeba-like animals with the simplest body organization of all known animals.
What is a key characteristic of Cnidaria (jellyfish, corals, sea anemones)?
They possess stinging cells (cnidocytes) for capturing prey and exhibit radial symmetry.
What is unique about Ctenophora (comb jellies)? (2)
they have rows of cilia for movement and use sticky cells (colloblasts) to capture prey, lacking stinging cells.
What are the defining features of Bilateria (most other animals)?
Bilateral symmetry and three germ layers (triploblastic).
What is radial symmetry?
Body parts are arranged around a central axis, allowing for multiple planes of symmetry.
What is bilateral symmetry?
The body can be divided into two mirror-image halves along a single plane (sagittal plane), resulting in distinct anterior, posterior, dorsal, and ventral sides.
What is biradial symmetry?
A combination of radial and bilateral symmetry, with four parts matching opposite sides but not adjacent sides.
What is spherical symmetry?
The body is shaped like a sphere, and any plane passing through the center divides it into two identical halves.
What is no symmetry?
The body has no specific symmetry or pattern, and parts are irregularly arranged.
How do most animals reproduce?
Most animals reproduce sexually by producing haploid gametes (sperm and egg) that fuse to form a diploid zygote.
What are the characteristics of sperm? (3)
Small, motile, and produced in large numbers.
What are the characteristics of eggs? (3)
Large, non-motile, and provide nutrients for the embryo.
What is ZW sex determination in reptiles?
ZW = female and ZZ = male.
What is budding?
A new individual grows off the parent and detaches, seen in hydra and corals.
What is fragmentation?
A piece of an animal breaks off and regenerates into a new individual, common in starfish and some worms.
What is parthenogenesis?
Development of an unfertilized egg into a new organism, seen in insects, some reptiles, and fish.
What happens during cleavage in embryonic development?
Rapid mitotic cell division without growth, forming blastomeres.
