Life Cycles Significant changes in structures over time
Life Cycle Objectives
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Compare and contrast mitosis and meiosis, including the role of DNA replication, where these processes occur in an organism, and why the processes are significant.
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Outline the life cycles of various species, indicating when mitosis and meiosis occur.
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Provide the characteristics of amphibians, including physical traits, life cycles, representative species, and typical habitats.
Cells have to replicate themselves: a fertilized egg has to become many cells, damaged cells have to be replaced, and sperm and egg have to be produced to form the next generation of life.
The processes of mitosis and meiosis are involved in the production of new cells.
A detailed look at both mitosis and meiosis, comparing and contrasting these processes.
A different model is used to compare mitosis and meiosis.
Can you describe what mitosis and meiosis have in common and also how they differ?
This small brittlestar is re-growing lost legs. Is this an example of mitosis or meiosis?
Mitosis and meiosis occur at different stages in an organism’s development.
This video is a microscopic look at the eggs and sperm produced by meiosis.
In the next section, we’re heading to wetlands to learn about amphibians and their complex life stages.
Amphibians are an excellent model for studying life stages.
We’ll start with a quick overview of amphibian characteristics, followed by a little more depth and links to life stages.
This video focuses in on key features that separate amphibians from other vertebrates.
Eryops, one of the earliest amphibians, is believed to have reached 10 feet in length.
Frogs and toads are the most common amphibians, but their names can be misleading.
Terminology is often constructed for ease of communication, but misconceptions can result.
One of the first biology lessons in elementary grades is on the frog life cycle.
Fill in a few gaps and learn why this is such a popular topic.
Tadpoles are breathing with gills underwater, although they are not always found in typical ponds and streams. See them is a more extreme location in this video.
Amphibians are not as frequently kept as pets as other vertebrates for a variety of reasons. This includes bans on sales due to over-collection and also concerns that released pets could become invasive species in new locations. Additionally, not all amphibians are easy to breed or maintain in captivity.
One relatively easy to care for amphibian is the freshwater Dwarf African Frog (Hymenochirus curtipes). The adults stay submerged, rising to the water surface to breath with their lungs.
New frogs showing color variation. The albino frog has two recessive alleles, which shut down another gene that would typically code for pigment production.
One month later, the frogs have grown. Notice the size of their abdomens. They require a variety of live foods for healthy growth and longevity.
A pet increasing in popularity is the Axolotl, also known as the “Mexican Walking Fish.” This is a large salamander that stays aquatic as an adult, relying on external gills for breathing.
Axolotls are close to extinction in the wild due to loss of habitat and water pollution. They require careful care in captivity and efforts are underway to try to save the species; in part due to their unique genome which has 10 times the genetic information as the human genome.
Axolotls have have a variety of naturally occurring colors due to variation in alleles. These animals are separated to minimize the chance of injury.
This is a genetically engineered neon axotoyl. It has genes from a jellyfish, which enables it to produce fluorescent proteins not naturally found in this species.
The red-eyed tree frog is one of the best known amphibian species.
Now that you have completed this section, list five characteristics of amphibians like this frog.
The next section demonstrates how tree diagrams are used to represent the ancestry and relatedness of different species.
Check your knowledge. Can you:
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compare and contrast mitosis and meiosis, including the role of DNA replication, where these processes occur in an organism, and why the processes are significant?
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outline the life cycles of various species, indicating when mitosis and meiosis occur?
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provide the characteristics of amphibians, including physical traits, life cycles, representative species, and typical habitats?
Go back to the Chromosomes & DNA Page
Go forward to the Genes & Development Page
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