In the world:

• Lizards - 4765
• Snakes - 2978
• Turtles - 307
• Amphisbaenians (not found in Australia) - 165
• Crocodiles - 23
• Tuatara - 2

In Australia:

• Lizards - 619
• Snakes - 192
• Turtles - 34
• Crocodiles - 2

Yes! You will generally need to get a licence. See our Reptiles as pets page for more information.

Opinions will differ, but I think one of the Children's python group is the best beginner snake species.

This depends on what you mean by "largest".

Longest snake in the world
Reticulated python (Python reticulata)

Heaviest snake in the world
Anaconda (Eunectes murinus)

Longest snake in Australia
Probably the scrub python (Morelia kinghorni)

That depends on what you mean by "deadliest".

Snake with the most toxic venom (when tested on mice)
Inland taipan (Oxyuranus microlepidotus).

Snake that causes the most deaths in Australia
Eastern brown snake (Pseudonaja textilis).

Snake that causes the most deaths in the world
Probably the saw-scaled viper (Echis carinatus) or the Russell's viper (Daboia russelii).

List of snake venom toxicities
Here is a list of some snake species, ranked by venom toxicity (tested in mice). All snakes are Australian, except the four labelled otherwise.
Tiger snake taxonomy is currently the subject of debate. The scientific names used here are taken from the original research article.
Toxicity is measured as an LD₅₀. The LD₅₀ test is a way of determining the relative toxicity of a venom. Increasing doses of venom are administered to a group of test subjects (normally laboratory mice). The dose at which half of the test subjects die is the LD₅₀ for that venom and route of administration (normally sub-cutaneous). Below is a table of LD₅₀ results for various snake venoms tested on mice. It should be noted that other snakes have since been tested, but are not included here. This table is only here to provide a relative measure of the toxicity of venom. This table is based on data from the following publication:

Broad, A. J., S. K. Sutherland and A. R. Coulter. (1979) The lethality in mice of dangerous Australian and other snake venom. Toxicon 17:661-664.

According to the list, the inland taipan has the most toxic venom of any snake tested. The eastern brown and the coastal taipan come in at numbers two and three respectively. These figures have come from LD₅₀ tests that used rodents, the very prey item these three snakes specialise in eating. As such, it should be remembered that these test results provide only a relative measure of a snake's toxicity to mice.

Note: this is not a list of the top 25 most toxic snakes. Not every snake in the world has been tested. This list is just comparing the venom toxicities of these 25 snakes.

Yes! Snakes (and all reptiles, birds, amphibians, monotremes and marsupials) have a vent called a cloaca at the base of their tail that they use for defecation (that's the technical term for dropping a log). The cloaca is a single opening that they use for both excretion and reproduction. The frequency with which a snake needs to defecate will depend on how much it's been eating, and the temperature. Warmer temperatures and lots of food will mean they need to go more often than a snake at a lower temperature that doesn't eat very often.

Here's a photo of faeces from a captive carpet python. The brown part is undigested food; the captive python was fed rats, so there's a lot of rat fur in there. The white part is made up of uric acid. Snakes (and lizards) don't urinate the way mammals do. Instead, they get rid of their 'urine' in solid form. This means they don't have to use a lot of water to get rid of their waste.

Different words are used around the world to describe these animals (collectively called "tortles"). Here in Australia we generally use these words thusly:

Tortoise
Land-dwelling tortle.

Turtle
Water-dwelling tortle. This can further be broken down into sea turtles and freshwater turtles. (But if you referred to a "freshwater tortoise", people would know what you're talking about.)

Terrapin
An American term for a freshwater tortle.

That depends on what you mean by "deadliest".

Snake with the most toxic venom (when tested on mice)
Inland taipan (Oxyuranus microlepidotus).

Snake that causes the most deaths in Australia
Eastern brown snake (Pseudonaja textilis).

Snake that causes the most deaths in the world
Probably the saw-scaled viper (Echis carinatus) or the Russell's viper (Daboia russelii).

List of snake venom toxicities
Here is a list of some snake species, ranked by venom toxicity (tested in mice). All snakes are Australian, except the four labelled otherwise.
Tiger snake taxonomy is currently the subject of debate. The scientific names used here are taken from the original research article.
Toxicity is measured as an LD₅₀. The LD₅₀ test is a way of determining the relative toxicity of a venom. Increasing doses of venom are administered to a group of test subjects (normally laboratory mice). The dose at which half of the test subjects die is the LD₅₀ for that venom and route of administration (normally sub-cutaneous). Below is a table of LD₅₀ results for various snake venoms tested on mice. It should be noted that other snakes have since been tested, but are not included here. This table is only here to provide a relative measure of the toxicity of venom. This table is based on data from the following publication:

Broad, A. J., S. K. Sutherland and A. R. Coulter. (1979) The lethality in mice of dangerous Australian and other snake venom. Toxicon 17:661-664.

According to the list, the inland taipan has the most toxic venom of any snake tested. The eastern brown and the coastal taipan come in at numbers two and three respectively. These figures have come from LD₅₀ tests that used rodents, the very prey item these three snakes specialise in eating. As such, it should be remembered that these test results provide only a relative measure of a snake's toxicity to mice.

Note: this is not a list of the top 25 most toxic snakes. Not every snake in the world has been tested. This list is just comparing the venom toxicities of these 25 snakes.

Yes! Traditionally only two species of venomous lizards have been recognised, the gila monster (Heloderma suspectum) and the beaded lizard (Heloderma horridum).

But more recently, researchers have announced they've discovered venom in a wide range of lizards, such as bearded dragons and goannas. You can read more about this research on Dr Bryan Fry's web site.