Opisthokonta (pt 1)

Choanoflagellates — closest relative to animals

• Extant group that is model for last unicellular ancestor of animals

• Both free-living and colonial species

• Ovoid or spherical cell body

• Single flagellum

• Collar of microvilli engulfs food particles

Animals (Metazoa) are

• Multicellular eukaryotes that lack cell walls

• Heterotrophic

• Most have nerve and muscle cells (Porifera**, Cnidaria*)

• Mostly reproduce sexually

Animals ingest their food

• suspension feeding

• bulk feeding

• fluid feeding

Intracellular Digestion

Ex. Porifera

Food particles flow through ostia (s. ostium) and flows out osculum

Intracellular digestion (via flagellated choanocyte cells)

choanocytes: collar of microvilli and single flagellum- create water flow and trap food particles

Extracellular digestion

Ex. Cnidaria

Tentacles encircle mouth and aid in food capture (incomplete gut)

Extracellular digestion (via enzymes in gut)

Intracellular digestion (via nutritive-muscular cells)

Lepidoptera (Insecta, Hexapoda, Arthropoda)

bulk feeding

Porifera

filter feeding

Most animal groups have cell types organized into tissues, which are organized into systems

Sensory system

• Detect prey

• Capture prey

Movement system

• Approach prey

• Subdue prey

• Ingest prey

Circulatory/ Respiratory system

• Move oxygen, nutrients, and waste

Sensing system = nervous system 

Nerve cells rapidly convey messages from one cell to another

• alert the animal to environmental stimuli 

• enable the animal to respond with coordinated movements

Animal Reproduction

Internal fertilization :

Sperm unites with the egg inside of the adult

External fertilization :

Egg and sperm unite outside of the adult

Monoecious :

One individual produces both M and F gametes

Dioecious :

One individual produce either M or F gametes

Neuron

nerve cells stimulated by electrical/ chemical signals to transmit information between different areas of brain and rest of nervous system

Sensory neurons

carry information from sense organs to brain

Motor neurons

transmit information from brain to muscles

Almost all animals reproduce sexually*

*Some can switch sexes or reproduce asexually

• Zygote:

  • Fusion of two haploid gametes

    • Large maternal gamete (egg or ovum)

    • Small paternal gamete (sperm)

  • Results in a diploid (2n) zygote

    • Contains 2 alleles of each gene