2C1 Life Cycles in Organisms

Question 1

What is a life cycle?

Answer 1

The series of changes an organism undergoes from fertilization to death.

Understanding life cycles helps in studying organism development, ecological interactions, and evolutionary adaptations.

Question 2

Distinguish between a simple life cycle and a complex life cycle.

Answer 2

• Simple life cycle: involves stages without drastic physical, behavioral, or environmental changes.
• Complex life cycle: includes significant morphological, behavioral, or habitat changes between stages.

Question 3

What are the three main stages of a plant/animal life cycle?

Answer 3

1. Fertilised egg (or seed)
2. Juvenile
3. Adult

Question 4

Give an example of an organism with a simple life cycle.

Answer 4

A flowering plant, where the stages involve seed, seedling, and mature plant.

Question 5

What are the four stages of the mammalian life cycle?

Answer 5

1. Fertilized egg
2. Infant
3. Adolescent
4. Adult

Question 6

What distinguishes mammals in their life cycle?

Answer 6

Mammals share traits such as body hair, separate sexes, and feeding young with mammary glands.

Question 7

Name an example of a marsupial with a unique life cycle.

Answer 7

Kangaroo, where young develop in a pouch after a short gestation period.

Question 8

List the five main stages of the human life cycle.

Answer 8

1. The fertilized egg (0-9 months in utero)
2. Infancy (0-3 years old)
3. Childhood (3-10 years old)
4. Adolescence (10-19 years old)
5. Adult (20+ years old)

The human life cycle stages can vary slightly based on cultural definitions of adolescence and adulthood.

Question 9

What marks adolescence in humans?

Answer 9

• Puberty.
• Significant physical and mental growth.

Question 10

What are the two main types of insect life cycle patterns?

Answer 10

1. Holometabolous metamorphosis.
2. Hemimetabolous metamorphosis.

Insects with hemimetabolous metamorphosis often show gradual changes between nymph and adult stages.

Question 11

Describe holometabolous metamorphosis.

Answer 11

It includes egg, larva, pupa, and adult stages, seen in butterflies.

Question 12

Describe hemimetabolous metamorphosis.

Answer 12

It involves egg, nymph, and adult stages, without a pupal stage, seen in grasshoppers.

Question 13

Name the five stages in the life cycle of a fish.

Answer 13

1. Egg
2. Larva
3. Fry
4. Juvenile
5. Adult

Question 14

Do fish typically fertilize their eggs internally or externally?

Answer 14

Most fish fertilize their eggs externally.

Question 15

What are the five main stages in the life cycle of a frog?

Answer 15

1. Egg
2. Tadpole
3. Tadpole with legs
4. Froglet
5. Adult frog

Frogs undergo metamorphosis from aquatic tadpoles to terrestrial adults, adapting to dual environments.

Question 16

How do frogs fertilize their eggs?

Answer 16

Through external fertilization during amplexus.

Question 17

List the four major stages in the life cycle of birds.

Answer 17

1. Egg
2. Hatchling
3. Fledgling (chick)
4. Adult

Question 18

What unique behavior do most birds exhibit during incubation?

Answer 18

They incubate their eggs by sitting on them.

Question 19

What are the three main stages in the life cycle of a flowering plant?

Answer 19

1. Seed
2. Seedling
3. Mature plant

Question 20

What is double fertilization in flowering plants?

Answer 20

It involves one sperm fertilizing the egg and another uniting with polar nuclei to form endosperm.

Question 21

Describe the process of seed production in flowering plants.

Answer 21

Seeds develop from fertilized ovules within the flower.

Question 22

What are angiosperms?

Answer 22

The most complex and evolved forms of plant life are the angiosperms, or the flowering plants.

Angiosperms are also the most common form of plant life on Earth today — there are over 270,000 different species of flowering plants (in contrast, there are only approximately 5,500 species of mammals on Earth).

Question 23

What are the distinguishing characteristics of angiosperms in their life cycle?

Answer 23

They produce seeds enclosed within fruits derived from carpel tissue.

Angiosperms dominate terrestrial ecosystems due to efficient seed production and varied pollination strategies.

Question 24

How do the vast majority of insects reproduce?

Answer 24

Sexually.

A very small percentage of insects reproduce asexually, meaning that they encompass both male and female parts, or that they do not need a partner to reproduce. However, most insects reproduce sexually, meaning a male and female are needed to reproduce.

Question 25

In terms of **mates**, explain how **birds are unique** to the animal kingdom.

Answer 25

Most birds are monogamous, meaning that they have only one sexual mate during any given mating period. ## Footnote Some will only have one mate through their entire life cycle.