Biology

Immortal Animals

Sat, 06 Dec 2025 10:09:09 GMT

Here are some of the most famous examples of animals considered “biologically immortal” or nearly so:

1. Turritopsis dohrnii (Immortal Jellyfish)

This tiny jellyfish can revert its cells to an earlier stage (a polyp) when stressed or injured.
Essentially, it resets its life cycle, making it theoretically immortal—though it can still die from disease or predation.

2. Hydra

A small freshwater organism that continuously regenerates its cells.
It doesn’t show signs of aging because its stem cells keep dividing indefinitely.

3. Planarian Flatworms

Known for remarkable regeneration—they can regrow entire bodies from fragments.
Their stem cells and telomerase activity make them resistant to aging.

4. Certain Bacteria & Archaea

Some microbes can form spores and survive for millions of years in dormant states.
They’re not “immortal” in the usual sense but can persist almost indefinitely under the right conditions.

5. Lobsters

As we discussed, they have active telomerase and don’t show typical aging signs.
They eventually die from external factors like disease or molting complications.

6. Greenland Shark

Lives 400+ years, making it the longest-lived vertebrate known.
Not immortal, but its aging process is extremely slow.

Scientists Just Discovered Dinosaur Cells That Have Survived 68 Million Years

Sun, 23 Mar 2025 09:13:30 GMT

https://www.msn.com/en-au/news/other/scientists-just-discovered-dinosaur-cells-that-have-survived-68-million-years/ar-AA1Bbe8K

Australia's Fertility Rate Pre and Post Covid

Sat, 14 Jan 2023 11:19:22 GMT

https://blog.id.com.au/2022/population/population-trends/australias-birth-rate-increases-for-the-first-time-in-10-years/

Bateman's principle

Sat, 02 Mar 2019 10:39:28 GMT

https://en.wikipedia.org/wiki/Bateman%27s_principle

What animals display the least sexual dimorphism?

Sat, 02 Mar 2019 10:34:24 GMT

Many bird species have very little sexual dimorphism. It takes an expert breeder to tell male and female peach-faced lovebirds apart, for example, and they have to do it by palpating the pelvic bone and judging from the width of a pelvis which sex the bird is. Even that has a degree of subjectivity and guesswork, and they’re not always right. Mockingbirds, which I’ve studied, are another example. In the spring-summer, the only way to tell a male from a female is that only the male sings, but in the fall-winter, both sexes sing equally and even that means of distinguishing them is lost.

Generally speaking, the more socially monogamous a bird species is, the less sexual dimorphism there is. In highly polygynous species (one male mating with multiple females), such as mallards, peafowl, and birds of paradise, there is much more sexual dimorphism.

Which is male and which is female in these lovebird and mockingbird pairs; can you tell? I can’t. Nor can an ornithologist, without either dissecting them or watching for behavioral differences.

Source: https://www.quora.com/What-animals-display-the-least-sexual-dimorphism