1 . Most birds, in particular, exhibit some degree of patterns and colours. Australia’s zebra finch (斑胸草雀), for example, was so named because of the zebra-like black and white bars on its tail. But it also has many other colours and patterns, from a bright orange bill to fine white spots along its reddish-brown sides. It’s not uncommon to spot the bird in the drier parts of Australia.

We tend to suppose all individuals of that species have their spots and bars in the same places. Look closer yet we’ll see that the quantity and design of these patterns vary between individuals. And somehow a bird exhibits a more obvious feather variation. Occasionally, we see one that has larger than usual pale areas of feathers or, more rarely, has lost its normal patterning altogether.

Colouration and patterning in all animals are caused by a range of pigments (色素). Melanin (黑色素) is responsible for blacks and browns, and a lack of this pigment can cause a partial or total loss of an individual’s dark patterning. The two main terms that describe these abnormalities are albinism and leucism. Both conditions are genetic and both can lead to a very similar physical appearance. Leucism, however, causes a lack of the pigment cells that produce melanin. But albinism causes the production of melanin to be reduced or absent.

Can we distinguish between the two conditions without the help of a cellular biologist? Yes. Albino animals have fully unpigmented red eyes. Leucistic animals, on the other hand, never completely lose pigment from the eye, although they can have blue eyes due to a partial loss of pigment.

Why don’t we see more albino or leucistic birds? Because the lack of melanin reduces the strength and lastingness of the affected birds’ feathers, making them more easily broken. Additionally, the birds’ vision and hearing are negatively affected, making them less able to hunt. The brighter feathers and lack of patterning also make them easier for attackers to see.

3 . Over 20%of Reptile Species Are Endangered

Reptiles are egg-laying animals with backbones and scaly (鳞状) skin. Examples of reptiles include animals like snakes, lizards, and crocodiles. Reptiles are cold-blooded, which means their bodies have the same temperature as the area around them.

A recent scientific report on a new study has revealed some unhappy news — 21% of all reptile species are in danger of extinction. That’s over 1,800 species in all. And at least 31 species of reptiles have already gone extinct.

The main reason these reptiles are faced with extinction is that humans are taking over more and more of their habitats — the places where they naturally live. More land continues to be cleared to make room for cities and towns. Large areas of land are also being cleared so that they can be used as farmland. Logging — cutting down trees for wood — is another big threat to reptile habitat.

When they think of reptiles, many people may think of hot, dry areas. But some of the most endangered reptiles live in forests. The new study reports that 30% of reptile species that live in forests are at risk of dying out. Turtles and crocodiles are among the most threatened reptiles — 60% of turtle species and 50% of crocodile species are at risk of extinction. Humans are a direct threat here, often killing these animals for their skin or meat.

But even if reptiles aren’t considered adorable, they play a very important part in the nature’s food chain. One service performed by reptiles that humans should appreciate is helping control certain pests (害虫) , like insects and rats.

Scientists say the good news is that we know what must be done to protect reptiles. Bruce Young, one of the leaders of the study, says, “We have all the tools we need.” Protecting natural areas, especially rainforest, is at the top of the list. Studies show that saving natural areas doesn’t just protect mammals (哺乳动物) or birds, but all kinds of animals, including reptiles.

5 . If you’re new to San Francisco, paying the city a visit, or simply looking for a new playground for you and your dog, here are four of the finest dog parks in San Francisco.

Corona Heights Dog Park

Often visited by residents from all over the city because of its nearness to the Randall Museum, Corona Heights Dog Park offers pets and owners breathtaking view after a steep hillside climb, and a fenced dog area that allows dogs to let loose without a leash (狗链). Owners will also enjoy the playground, tennis courts and basketball courts.

Dolores Dog Park

The grounds of Dolores Park once served as camps for those who were left homeless by the 1906 earthquake, but now are often visited by crowds of Mission District people. Four-legged friends can also wander about care free off-leash while making friends with other members of the doggie community.

Pine Lake Dog Park

Famous for its place as a rest stop for hundreds of species of birds to fly to and from warmer climates, Pine Lake Park is also prized by city dogs and their owners for their nice hiking paths, picturesque lake suited for swimming, and off-leash area on the park’s west end that lets dogs run free.

Buena Vista Dog Park

With a history of 146 years, Buena Vista Park is San Francisco’s oldest park. Dogs and owners with plus energy will love burning it on this park’s steep paths and winding staircases. Dog owners should have good control over their dogs, as it’s quite easy for dogs to get separated when going through Buena Vista’s many twists and turns.

Herds of elephants used to live on the plains of Africa and in the forests of Asia. But today, hunters are a serious danger     1     them.     2     large amount of cruel hunting has contributed     3     the dramatic     4     (reduce) of these large animals. To save them, some     5     (reserve) have been established where they can live in peace and safety. Moreover, many people are devoted to     6     (protect) them. However, the     7     (cruel) on them will continue as long as interest in buying elephant products     8     (permit). To make humans and animals live in harmony, it is urged that measures     9     (take) to protect these beautiful creatures from     10     (extinct).