An animal develops from a single-celled zygote into a complex multicellular organism through a coordinated sequence of events. Cell-to-cell signaling and differences in gene expression guide this process, allowing cells to specialize and form tissues and organs.
Fertilization occurs when an egg and sperm fuse to form a zygote. Each gamete is haploid, so their genetic material combines to establish a diploid genome. In mammals, the egg is surrounded by the zona pellucida, which helps protect it.
All flashcards
What is fertilization?
Fertilization is the fusion of egg and sperm, followed by union of their haploid nuclei to form a diploid zygote.
What are the fast and slow blocks to additional sperm entry?
The fast block is a rapid change in the egg's membrane potential. The slow block involves a change in the egg membrane's structure; egg-released proteins also help prevent other sperm from fusing.
What are the inner cell mass and trophoblast?
They are the two main cell populations of the mammalian blastocyst. The inner cell mass develops into the embryo; the trophoblast helps with implantation and contributes to the placenta and embryo nourishment.
What happens during gastrulation?
Cells rearrange and migrate as the blastula folds inward, forming a gastrula organized into the three germ layers: ectoderm, mesoderm, and endoderm.
How do chemical signals contribute to organogenesis?
Signals from a cell's embryonic environment influence gene expression. The resulting patterns of gene expression help cells differentiate and contribute to particular tissues and organs.
Quiz questions
What is formed when the haploid nuclei of an egg and sperm unite?Answer: A diploid nucleus in the zygote.
What role does the sperm acrosome play during fertilization?Answer: It contains enzymes that help the sperm pass through the egg's outer barrier.
How does the trophoblast contribute to early mammalian development?Answer: It aids implantation and contributes to the placenta and embryonic nourishment.
A developing embryo has begun folding and moving cells into three layers. Which process is occurring?Answer: Gastrulation.
Which embryonic germ layer gives rise to muscle cells and connective tissue?Answer: Mesoderm.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.