UNIT 9 Interaction and Reproduction

UNIT 9. FUNCTIONS OF LIVING THINGS

INTERACTION AND REPRODUCTION

1. FUNCTION OF REPRODUCTION

Reproduction is the set of processes which function to continue the species.

2. REPRODUCTION IN ANIMALS

Depending on the complexity of the animals, they can be reproduced by three mechanisms:

Asexual reproduction: it is performed by poorly developed animals, and new organisms are produced from a single parent in one of two processes:a) Fragmentation: typical starfish, where a fragment can lead to a new individual.

b) Budding or gemmation: typical of sponges and corals. Buds appear in the parent, resulting in a new individual. It can be attached to the parent and form a colony, or separated and isolated individuals are formed.

Sexual reproduction: most animals have this type of reproduction, and usually have separated sexes. A female individual, with a female gonad or ovary produces female gametes or eggs, and a male individual with a male gonad or testicles produces male gametes or sperm. The union of egg and spermatozoon cell generates a new egg cell or zygote, which will lead to a new individual with a mix of the characteristics of both parents.Some species are hermaphroditic, and the same individual has two gonads, sometimes acting as male and sometimes as female. This is the case in worms or snails.

Alternant reproduction: It is typical of jellyfish or cnidarian. Where some generations are formed by budding and others alternating to produce male and female cells which originate a zygote by sexual reproduction.

3. THE REPRODUCTION IN PLANTS

Plants can make 3 types of reproduction:

Asexual reproduction: from a single plant will make another equal to the first. This can be achieved by several mechanisms, including:a) Bulbs: as onions or garlic.b) tubers or underground stems: as the potato.c) Stolons: like strawberries. They are trailing stems that take root when they contact with the ground and form a new plant.d) Stems: as geraniums, stems from being introduced into the earth.e) Grafts: as the pear trees or roses, where the trunk of a species (rose) introduces a stalk of another variety (wild rose) and forms a more resilient intermediate variety.

Sexual reproduction: Characteristic of flowering plants, which takes place in the same flower. The male reproductive are the stamens and the gynoecium is the female where the eggs are fertilized and form seeds.

Alternant reproduction: It is typical of non-flowering plants such as mosses and ferns. In both plants alternating two individuals, one formed from an asexual spore called gametophyte, which produces sex cells that generate zygote. When these germinate it gives rise to another individual named sporophyte, which produces asexual spores.

4. FUNCTION OF INTERACTION

It is the set of processes to obtain outside information in order to develop appropriated responses.

5. INTERACTION IN ANIMALS

It is performed by the nervous system and endocrine system.The nervous system consists of three types of organs: a) Receptor organs that catch information from outside. They are the sense organs (sight, smell, taste, hearing and touch) , which receive light, chemical, thermal, mechanical stimulis, and so on. b) Coordinating organs which process information and develop appropiate responses. They are the brain (controls intelligence, memory, etc.), cerebellum (controls voluntary movements such as running, picking things, etc), medulla (control function of the heart, lungs, etc.), spinal cord (control reflex actions, such as closing the eyes when somewhere enters), and nerves.

c) Effector organs that develop the answers. These are the muscles and glands.

The endocrine system consists of a set of endocrine glands that produce chemical substances called hormones, which travel through the blood and reach all the organs, but only act in certain organs called target organs. The endocrine system is responsible for changes in animals, such as the metamorphosis of insects or frogs.6. INTERACTION IN PLANTS

Plants have not got a nervous system but do have endocrine system, which allows them to interact with their environment. Although plants cannot move, they can make small movements. These can be of two types: a) Tropisms: movements that are influenced by the direction of the stimulus. For example, the movement of sunflowers following the sun (fototropisms), growth of roots down into soil (geotropisms). b) Nastics: movements that are not influenced by the direction of the stimulus. For example, mimosa leaves retract when touched.

ACTIVITIES OF REPRODUCTION:

1. What is the main difference between sexual and asexual reproduction?

2. Describe :

a) animal fragmentation.

b) Example of:

fragmentation

Budding or gemmation.

3. Most jellyfish pass through two life phases during their life cycle. Make a drawing to illustrate this.

4. Research examples of sexual dimorphism. Then describe the animals:

The female is brown and small. The male is larger with bright colours.

5. Which of the following statements correspond to sexual or asexual reproduction?

a) the descendant is identical to the progenitor.

b) Organisms which grow in soil.

c) this requires two organisms.

d) formation of gametes.

e) Fertilisation must occur.

f) The descendants characteristics are a mix of both progenitors.

g) Diversity among individuals of a species.

h) An individual organism can generate many descendants.

ACTIVITIES OF INTERACTION:

1. What is interaction? What elements does interaction involve? Copy and complete:

Interaction is...

Stimulli Receptors...........................

Detectable changes in the internal of external environment

2. Which sense organ detects chemical substances in air?

3. Can you solve these sense organ riddles?

This organ is used by...

a) arthropods to smell things.

b) fish to detect temperature changes.

c) most animals to detect pressure.

d) some animals to distinguish sounds.

4. Which of the senses of a mammal provides more information about the environment? Why?

5. The gazelle hears the cheetah.

a) what other two senses does the gazelle use to detect the presence of the cheetah?

b) which sense do you think is most developed in the gazelle? Give a reason for your answer.